Spinoza on Inherence, Causation, and Conception
Yitzhak Y. Melamed (Johns Hopkins University)
(Forthcoming in Journal of the History of Philosophy)
	Spinoza’s philosophy is bold and rich in challenges to our “common-sense intuitions”, and insofar as it provides powerful arguments to motivate these challenges, I believe that we cannot ask for more. Bold and well-argued philosophy has the indispensable virtue of being able to unsettle and try us, to move us to reconsider what seems natural and obvious, and possibly even to change our most basic beliefs. Indeed, for those who seek to test – rather than confirm - their old and well-fortified intuitions, Spinoza is nothing short of a living spring.
	My deep support for rigorous, counter-intuitive philosophy notwithstanding, a considerable part of the current paper will be dedicated to an examination and critique of one of the boldest and most fascinating readings of Spinoza of the past few years. In his recent piece, “Rationalism Run Amok: Representation and the Reality of Emotions in Spinoza,” and in his outstanding new book, Michael Della Rocca suggests a strict identification of the relations of inherence, causation, and conception in Spinoza (Della Rocca develops this view partly in response to a position recently articulated by Don Garret). In order to see the striking implications of this claim, one need only realize that, according to Della Rocca, Spinoza holds that insofar as the sun is the (partial) cause of some states of the sunflower, the sunflower (partly) inheres in the sun. Furthermore, insofar as my great-great-grandparents caused me, I inhere in them (though we never co-existed at the same time). The mere oddity of Della Rocca’s claim will play only a limited role, if any, in my discussion below. Della Rocca provides important and interesting arguments to the effect that if we are to accept Spinoza’s radical version of the Principle of Sufficient Reason (henceforth, PSR), we should bite the bullet and accept the odd implications of Spinoza’s alleged view. While I have nothing but admiration for this willingness to read Spinoza in an allegedly consistent and uncompromising manner, I do think that Della Rocca’s argument that a strict endorsement of the PSR leads necessarily to the identification of the relations of inherence, causation and conception is wrong. I will argue that (1) Spinoza never endorsed this identity, and (2) that Della Rocca’s suggestion could not be considered as a legitimate reconstruction or friendly amendment to Spinoza’s system because it creates several severe and irresolvable problems in the system, and for that reason (and not because the threefold identity contravenes common sense) it should be rejected. In the rest of the paper I rely on my analysis of the relations of inherence, causation, and conception, and suggest a new interpretation of core issues in Spinoza’s metaphysics, and particularly of the conceived through and in another relations and the nature of the substance/modes opposition. Against Della Rocca’s claim that the bifurcation of efficient causation (into causation which is, and is not, accompanied by inherence) constitutes an illegitimate brute fact, I will argue that the bifurcation of causation in Spinoza is paralleled by a bifurcation of conception and that the two relations are grounded in the foundational bifurcation of existence into substance and modes. If we are to recognize the reality of modes in Spinoza, we must also acknowledge the bifurcations that result from the bifurcation of existence into substance and modes.
	In the first part of the paper, I present the considerations and arguments that motivated Don Garrett’s and Della Rocca’s interpretations.  In the second part, I present and examine several problems that result from Della Rocca’s reading.  In the third and final part, I (1) present my own view on the relation among inherence, causation, and conception; (2) offer a new interpretation of the conceived through relation in Spinoza; and finally, (3) defend and justify the presence of (non-arbitrary) bifurcations at the very center of Spinoza’s system. 

	1. Inherence, Causality, and Rationalism

	E1a4, one of the most important yet enigmatic axioms of the Ethics, reads:
E1a4: Cognition of an effect depends on, and involves, the cognition of its cause [Effectus cognitio a cognitione causae dependet, et eandem involvit.].
While the precise meaning of this claim may be disputed, a consideration of Spinoza’s use of this axiom makes it clear that at least part of what it means is that
	(1) If x causes y, then y is conceived through x.
In E1p6, Spinoza argues that “One substance cannot be produced by another substance.” The second of Spinoza’s two proofs of this proposition reads: 
If a substance could be produced by something else, the cognition of it would have to depend on the cognition of its cause (by A4). And so (by D3) it would not be a substance (E1p6d2).
The first sentence of this passage relies on E1a4 to conclude from “x is the cause of y (or x produces y)” that “the cognition of y involves the cognition of x.” In the second sentence Spinoza argues that had the cognition of a substance involved the cognition of something else as its cause, this would violate the definition of substance (E1d3) as what is “conceived through itself, i.e., that whose concept does not require the concept of another thing.” Thus, in E1p6d2, Spinoza clearly reads E1a4 as stating that effects are conceived through their causes, i.e., (1). Following Don Garrett, I will call this doctrine the “Causality Implying Conception Doctrine.”
	In his 1996 book, Representation and the Mind-Body Problem in Spinoza, Della Rocca followed Jarrett, Bennett, and Wilson in pointing out that Spinoza’s use of E1a4 in E1p25d shows that he understands E1a4 to claim also the opposite direction implication, i.e., that 
(2) If y is conceived through x, then y is caused by x.
E1p25d reads:
E1p25: God is the efficient cause, not only of the existence of things, but also of their essence.
Dem.: If you deny this, then God is not the cause of the essence of things; and so (by A4) the essence of things can be conceived without God. But (by P15) this is absurd. Therefore God is also the cause of the essence of things, q.e.d.
The demonstration takes E1a4 to state, “if x is not the cause of y, y can be conceived without x.” The contrapositive of the last claim is that “if y must be conceived through x, x is the cause of y,” which is roughly (2). Following Garrett, we will call this doctrine the “Conception Implies Causality Doctrine.” The conjunction of (1) and (2) gives us the biconditional:
(3) x causes y, iff y is conceived through x.
	In 2003, Garrett published an important article offering a new interpretation of the doctrine of the conatus in Spinoza. According to Garrett, the phrase “quantum in se est” in E3p6 (“Unaquaeque res, quantum in se est, in suo esse perseverare conatur”) should be read literally, as implying that finite things can be in themselves to a certain degree (while God is unrestrictedly “in se”). In a note in this article Garrett claims:
It is clear that, in this context, Spinoza also accepts the converse claim that “if y is conceived through x, then y is in x.” This applies, however, only in cases where y is completely conceived through x.  For although a finite mode may be partly conceived through the other finite modes that are partial causes of it, it does not follow that it is in those finite modes.  Rather, it is in the substance through which it – as well as the finite modes that help to cause it – may be completely conceived.
Garrett also adds:
One might reasonably ask whether, if an accident is not entirely in the singular thing of which it is predicated, it must then be partly in the other singular things that contribute to its causation. Spinoza’s view seems to be that whatever is completely caused by x must be completely in x, but that we need not accept as a general principle that whatever is only partly caused by x is partly in x. That is, what Spinoza calls “immanent causation” implies inherence, but what he called “transient causation” does not.
Della Rocca is highly supportive of Garrett’s view that finite things can be in themselves to a certain degree. He also expresses sympathy for Garrett’s decision to propose a rather unstable position (i.e., by suggesting that finite things can be partly in themselves, but not partly in another) in order to avoid some bizarre implications, yet he thinks that Spinoza should bite the bullet and embrace the bizarre implications.
So on Garrett’s view, although conception and causation may be only partial, and although a thing can be only partly in itself, being in another is all or nothing.  This seems to be a reasonable move because it avoids having to bite the apparent bullet of saying that the table is in any way in or inheres in the carpenter. But Spinoza is not one to avoid biting bullets or, more accurately, what one might see as bullets the biting of which is to be avoided, Spinoza often sees as logical or rational conclusions to be embraced because of their rationality, because of their logical unavoidability. And, indeed, I think that there are good reasons to see Spinoza as embracing this conclusion.
Hence, Della Rocca suggests that we should unrestrictedly accept the Inherence-Causation Biconditional:
(4) x is in y, iff x is caused by y.
	In order to support (4), Della Rocca provides both textual evidence and a highly interesting argument relying on (Spinoza’s version of) the Principle of Sufficient Reason. Della Rocca reads Spinoza’s definition of mode – “E1d5: By mode I understand the affections of a substance, or that which is in another through which it is also conceived [Per modum intelligo substantiae affectiones, sive id, quod in alio est, per quod etiam concipitur]” – as stating the biconditional
	(5) x is in y, iff x is conceived through y.
We will call (5) the “Inherence-Conception Biconditional.” Obviously, from (3) and (5) one can deduce (4) by transitivity.
	Della Rocca brings some further textual support for (4) by pointing to an interesting parenthetical passage from the Theological Political Treatise that seems to imply that an effect is a property of its cause:
The more we know natural things, the greater and more perfect is the knowledge of God we acquire, or (since knowledge of an effect through its cause is nothing but knowing some property of the cause) the more we know natural things, the more perfectly do we know God’s essence, which is the cause of all things.
According to Della Rocca, the claim that knowledge of an effect through its cause is knowledge of a property of the cause can be read as implying that to be a property and to be an effect of x are one and the same thing. Della Rocca also cites another passage from the Short Treatise which suggests that the internality/externality of effects is a matter of degree (and hence that an effect can be partly in its cause and partly in an entity external to the cause):
All the effects which we produce outside ourselves are the more perfect the more they are capable of being united with us to make one and the same nature, for in this way they are nearest to internal effects.
	Yet, Della Rocca’s main motivation for accepting the Inherence-Causation Biconditional comes from the Principle of Sufficient Reason. It is commonly agreed that, for Spinoza, inherence implies causality; the point of contention is whether causality implies inherence. If causality does not imply inherence, it would seem that within causation there is a sharp division between causation which is accompanied by inherence and causation which is not. This bifurcation, like any other fact, demands an explanation, but according to Della Rocca, there is no explanation for this bifurcation: it is just a brute fact.
[A]s far as I can see, there is no good answer to the question in virtue of what does what might be called inherence-dependence differ from other forms of causal dependence. And, thus, this difference would seem to be a brute fact, in violation of the PSR. Given Spinoza’s deep aversion to brute facts, it behooves us to see Spinoza as not drawing this ultimately arbitrary distinction.  
Similarly, Della Rocca argues, insofar as (3) is true, the relations of causality and conception always go together. Now there is only one kind of conception, and it appears to be just a brute fact that conception (being always the same) is sometimes accompanied, sometimes not, by inherence.
But now on the conceptual level, what kind of dependence relations are there?  It seems that there is just one: the table is conceived through God and the table is conceived through the carpenter. In the former case, the conceptual dependence is complete; in the latter case, the conceptual dependence is not complete.  But in both cases, on the conceptual level, the kind of dependence seems to be the same.  There is no radical shift in kinds of dependence relations on the conceptual level as there is on the ontological level between dependence relations that are relations of inherence and those that are not.  Thus, on the view I am opposing, the homogeneity of the conceptual dependence relations is not matched – not, if you will, paralleled – by any homogeneity of the ontological dependence relations.
For Spinoza, brute facts are anathema, and if the only way to avoid the acceptance of brute facts is by endorsing the Inherence-Causation Biconditional (4), Spinoza, Della Rocca says, must bite this bullet.
	Let me state from the outset that I do not believe Spinoza himself actually accepted the Inherence-Causation Biconditional. The notions of inherence, causation, and conception are far too central to his system for him to have neglected stating their equivalence (or identity) had he believed in it. Spinoza makes abundant use of the notion of partial (or inadequate) cause, but as far as I can see, in none of these places does he indicate that a partial effect inheres (partly) in its (partial) cause.  I consider this simple point to be conclusive as to Spinoza’s actual views, though it still leaves open the possibility of a friendly amendment to, or even improvement of, his system. But let me add two more brief points about Spinoza’s actual views. When we look carefully at Spinoza’s use of Ed5, we find that he relies on this definition quite frequently but never uses it to derive inherence from conception. Finally, the first axiom of the Ethics could be read as excluding the possibility of one thing’s being partly in itself, partly in another.
E1a1: Whatever is, is either in itself or in another [Omnia, quae sunt, vel in se, vel in alio sunt].
If Spinoza’s use of ‘vel’ indicates mutually exclusive disjunctions, then E1a1 seems to reject the possibility of one thing being both in itself and in another. 
	Be that as it may, even if Spinoza himself never accepted the Inherence-Causality Biconditional, it appears to me perfectly legitimate to suggest an improvement of Spinoza’s system. Obviously, such an improvement should remain loyal to the principles and main contours of the system. In the following part of this paper, I consider the viability of the Inherence-Causality Biconditional as a Spinozistic doctrine and its consistency with the rest of Spinoza’s system, without regard to the question of whether Spinoza did or did not explicitly accept the doctrine.

	2. Bifurcations and the Principle of Sufficient Reason

	I see several problems with the Inherence-Causality Biconditional, and I will present them in escalating order (i.e., from least problematic issues to most).
	(i) In E1p18, Spinoza presents a distinction between immanent and transitive (or transient) causation.
E1p18: God is the immanent, not the transitive, cause of all things.
Dem.: Everything that is, is in God, and must be conceived through God (by E1p15), and so (by E1p16c1) God is the cause of [NS: all] things, which are in him. That is the first [thing to be proven]. And then outside God there can be no substance (by E1p14), i.e. (by E1d3), thing which is in itself outside God. That was the second. God, therefore, is the immanent, not the transitive cause of all things q.e.d.
From the demonstration of E1p18, we can learn that an immanent cause is an efficient cause (hence the appeal to E1p16c1) whose effect is in the cause (hence the invocation of E1p15). A transitive cause is an efficient cause whose effect is not in the cause. Now, according to Della Rocca, every effect is in its cause, and this seems to make the transitive cause into an empty category that is strictly impossible. While this objection puts some pressure on the threefold identity thesis, it may not be fatal. A proponent of the Inherence-Causation-Conception identity thesis could respond by suggesting that any case in which the effect is not fully in the cause should count as transitive causation (while immanent causation will be defined as the case in which the effect is fully in the cause). In such a case, the carpenter would only be a transitive cause of the table, since the table is only partly in the carpenter. We may press this objection a bit further. According to the threefold identity thesis, the table should be fully in its complete cause. Thus the table is perhaps not fully in the carpenter, but it should be fully in the singular thing constituted by the carpenter together with all the other entities which contributed to the production of the table (see E2d7). Hence, it would seem that the category of transitive causation still remains empty, since each thing would be fully in the singular thing which caused it. Della Rocca could respond to this by saying that a transitive cause is only an incomplete account of a case of immanent causation. In other words, we consider the carpenter the transitive cause of the table (since the table is only partly caused by the carpenter), but the carpenter together with all the other entities that collaborated in the causation of the table are (all together) the immanent cause of the table. I do not think this response works, since it seems to me that Della Rocca should say that that part, or aspect, of the table that is completely caused by the carpenter is also completely in the carpenter; and if this is the case, then, again, the category of transitive causation turns out to be empty.
	(ii) In E3d3, Spinoza defines an affect [Affectus] as the “affections of the Body by which the Body's power of acting is increased or diminished, aided or restrained, and at the same time, the ideas of these affections.” Now, consider the following scenario. Josephine whispers “bu” to Napoleon. Napoleon laughs. Insofar as Napoleon’s laugh is caused by Josephine, the laugh also inheres in Josephine, i.e., is an affection of Josephine’s body, as well as of Napoleon’s body. Laughter or joy increases our power of acting, but the question is: Whose power of acting is increased? Since both Josephine and Napoleon contributed to the causation of the laugh, we should, according to Della Rocca, ascribe the joy to both bodies. The tragic reality, however, is that in many a case Josephine-like people say bu-like things to Napoleons, making the Napoleons laugh (i.e., increasing their power of acting), while the Josephine-like people remain at the same level of power of acting, or perhaps even get saddened. In other words, causing an increase in the power of acting of someone else does not necessarily increase your own power of acting, but if we accept the identity of inherence and causation, it would seem that the increase of the power of acting must also belong to (i.e., be in) the cause of the increase as well. A world with such regularities would be quite interesting and, perhaps, just, but it is not ours, and we have no reason (or textual support) to believe that Spinoza thought that our world obeys such wonderful regularities.
	(iii) Durational Inherence – The next few arguments deal with the implications of Della Rocca’s thesis for Spinoza’s understanding of temporality. A radical reading of Spinoza, suggested primarily by the German and British Idealists, takes Spinoza to be a modern reviver of the ancient Eleatic philosophy. According to this reading, Spinoza denies the reality of finite things, time, and duration, and affirms the sole reality of the eternal substance in which all determinations are null and void. As I will later argue, I suspect that Della Rocca’s bold use of the PSR in order to obliterate any bifurcations in Spinoza’s metaphysics leads him toward this stance, but so far Della Rocca does not seem to subscribe to this view. Assuming that Della Rocca does not ascribe to Spinoza the view that duration (“duratio”) is illusory, it seems that insofar as future things are caused by past things, future things must also inhere in the past (i.e., in past things). But that is a very bizarre conception of inherence. Traditionally, inherence is understood as a simultaneous relation between a substratum and its states or qualities (or at least as a relation that is not spread in time, in the case of a substratum and states which are not in time at all). Of course, one may still bite the bullet by embracing this odd notion of inherence -- as I readily admit, Spinoza is always full of surprises -- but upon closer examination, it seems that Della Rocca’s understanding of inherence amounts to nothing over and above efficient causation. In 1969, Edwin Curley published a work that in many ways changed Anglo-American discourse on Spinoza. Curley argued that in Spinoza’s work, the Substance-Mode relation cannot be understood according to its traditional sense but rather that, for Spinoza, to be a mode of God is just to be caused by God. Over the years, Curley’s interpretation was criticized by several scholars, and in his recent work Della Rocca himself provides two powerful arguments against Curley’s position, claiming that “for Spinoza, all modes… are modes in something like the Cartesian sense: they are features or states of God.” Della Rocca explicitly aligns himself with the traditional understanding of inherence: “The notion of in-ness as manifested in the substance-mode relations, I believe, a version of the traditional notion of inherence: modes are in substance in the sense that they inhere in that substance.”  Yet, I am not aware of any text of Descartes or his predecessors in which inherence is taken as a relation that is spread in time.
	As far as I can see, Della Rocca’s view does not much differ from Curley’s. An inherence relation in which the substratum and qualities have different temporal locations seems to have very little in common with the traditional understanding of inherence (and much more in common with the traditional characteristics of efficient causation).  I have elsewhere provided several arguments against Curley’s interpretation of the substance-mode relation, and if Della Rocca’s is just the same view in different garb, I believe that many (though not all) of the same arguments are applicable to his reading as well. 
	(iv) Inherence in non-existing things? – An inherence relation that is spread in time has many bizarre implications. From the following passage from E1p17s we can conclude that (1) at least some things cease to exist and perish. If we add to that Spinoza’s claim in E1p36 that (2) all things have effects, it would seem that according to Della Rocca an effect of a mode that ceased to exist may still inhere in the mode after it ceased to exist. Suppose mode M caused (i.e., was a partial cause of) mode N at t0 and immediately afterwards at t1 ceased to exist. For Spinoza mode N could perfectly exist without its cause after t1.
A man is a cause of the existence of another man, but not of his essence, for the latter is an eternal truth. Hence, they can agree entirely according to their essence. But in existence they must differ. And for that reason, if the existence of the one perishes, the other’s existence will not thereby perish [si unius existentia pereat, non ideo alterius peribit]. But if the essence of the one could be destroyed and become false, the other’s essence would also be destroyed (E1p17s| II/63/18-23. Italics mine)
However, it would make no sense for N to exist after the perishing of M, were N to be in M (i.e., were N a mode or affection of M). The existence of a mode completely depends on its substratum (E1d5), and if the substratum perishes, the mode simply cannot exist without is substratum. In this sense, there is a sharp contrast between the relations of inherence and causation in Spinoza. An effect can exist after its cause perishes; a mode cannot exist after its substrate perishes. 
	(v) Bifurcation of Inherence I: Degrees of Reality. – One of the traditional features of the in alio relation is that modes are less real than the substratum in which they inhere. Modes completely depend for their existence on their substance and are therefore less real than substance.  Now, if we identify inherence and causation, it would seem that past things are more real than present and future things, and that the universe is winding down. If duration is not illusory, and the past causes the present and the future, then the past should also be the substratum in which the future and present inhere. If the future and present inhere in the past, then the past must be more real than the present and the future. Notwithstanding the counter-intuitive nature of such a view (and we have no prejudices in favor of commonsense!), it seems that Spinoza embraces a view according to which all moments in time “are equally dear to God” (to paraphrase the saying of the great German historicist, Leopold von Ranke). “Insofar as the mind conceives things from the dictate of reason, it is affected equally, whether the idea is of a future or a past thing, or of a present one,” says Spinoza in E4p62. Now, when the mind conceives things “from the dictate of reason” it conceives them adequately, and as such it does not prefer one point in time over another (E4p62d&s). Here, again, there is a sharp contrast between the relations of inherence and causation in Spinoza. A mode is always dependent upon and hence less real than its substratum, but Spinoza never claims that an effect is less real than the cause. One possible line of defense may suggest that in some cases inherence is accompanied by a difference in the degree of reality between the quality and its substratum (as in the case of substance and modes), while in other cases inherence does not involve a gap between the reality of the substratum and its qualities. The problem with the last suggestion is that it seems to create a bifurcation within inherence, a bifurcation which, as I will shortly argue, appears to be a brute fact.
	(vi) Bifurcation of Inherence II: Temporality. – Another bifurcation between two kinds of inherence in Della Rocca’s interpretation of Spinoza arises for the following reasons. For Spinoza, causal relations can be both in duration, and not in duration. The causal relation between God’s essence and the infinite modes is an example of non-durational causality (the effect does not come after the cause). The causal relation between the father of Napoleon and Napoleon himself is an example of the second kind of causality (the cause precedes the effect). Now, according to Della Rocca, this bifurcation of causation should be accompanied by a bifurcation of inherence so that some inherence relations are in time and others are not. But why is it the case that some inherence relations are in time, while others are not? Is this not a brute fact? Obviously, Della Rocca could resort to a strategy of claiming that if we are willing to accept the bifurcation of causality into temporal and non-temporal, we should also be content with a bifurcation of inherence. But I do not think that this response works. I suspect that, in Spinoza, there is a genuine bifurcation of causality (not of inherence), and I will soon attempt to explain the reason for this bifurcation in order to show that it is not a brute fact. On the other hand, Della Rocca, who is committed to the elimination of (unexplained) bifurcations, must explain the durational vs. non-durational bifurcation of both inherence and causation. As far as I can see, he has not yet provided such an explanation.
	(vi) “in alio” without “in se”? – I have previously argued that Della Rocca’s identification of causation with inherence results in making the past, in which the present and future inhere, more real than the future and present. But the story gets worse once we realize that Spinoza does not believe in creation in time and takes duration to be infinite both backwards and forwards. This would mean that the order of durational inherence (i.e., the inherence of effects in their past causes) goes backwards infinitely and is never grounded in an entity that is “in itself.” But what is “in another” depends for its very existence on something else (that’s what it is to be a mode!), and as long as we have an infinite chain of “in another” entities that are not ultimately grounded in an “in itself,” the existence of the whole chain remains up in the air, without explanation and grounding for its existence.
	Della Rocca would probably respond that, though it is true that an infinite chain of modes depending one upon the other must be ultimately grounded in a substance (for otherwise, modes will exist without substance, which is a plain contradiction for Spinoza), the fact that the modes are grounded in the substance in an inherence that is non-durational (insofar as each finite mode is part of an infinite mode that inheres in a non-durational manner in God) should free us from the worry that durational inherence is an infinite order that does not end by grounding in an ‘in se.’ 
	I still do not think that we should accept this answer. According to Della Rocca, each finite mode takes part in two kinds of inherence relation. On the one hand, each mode inheres (in a non-durational manner, as a part of an infinite chain of finite modes, or as part an infinite mode) in God’s nature or essence, but on the other hand, it also inheres, in a durational manner, in the singular thing that caused it. The result is that the poor mode becomes a servant of two masters, and the whole causal structure of Spinoza’s system gets distorted. If the durational inherence that Della Rocca accepts is genuine inherence, it cannot appeal to the fact that the modes are grounded in a non-durational inherence in the substance in order to explain how we can have an order of inherence (i.e., durational inherence) without an “in se.” We have here two distinct chains of inherence relations and each should be grounded independently of the other, if each is to be reckoned as bona fide inherence. If we resort to the position that one chain of inherence (the non-durational inherence of modes in God’s nature) is grounded independently, while the other chain of inherence (the inherence of finite modes in their finite causes) relies on the first chain in order to have grounding, we are faced again with a charge of bifurcating the inherence relation into two kinds: inherence that is grounded in an ‘in se,’ and inherence that is not. The very fact that durational inherence is not grounded in an ‘in se’ should make us strongly suspect that it is not a genuine inherence relation at all (and, as we have previously seen, we have several independent reasons that point to the very same conclusion).
	(vii) Modes as Tropes. – According to Della Rocca, a mode can inhere in two distinct things. If both Geppetto and Pinocchio build a table T, T inheres in both G and P. But is not a mode supposed to be completely dependent on its substratum (i.e., its substance)? If so, how can it be a mode of two substrata? Charles Jarrett and John Carriero argued convincingly (and independently) that Spinozistic modes are particular qualities, or tropes, of the substance. 
	A simple thought experiment might help us see why a mode cannot be shared by two substrata that are substances. Consider the alleged possibility of two substances A and B sharing a mode m. Let’s assume now that there’s a change in mode m. The cause of the change can come from either one of the two substances. However, if A is the cause of the change in m, it would seem that substance A caused a change in substance B (since m is also a mode of B), whereas Spinoza strictly rejects any causal interaction between substances (E1p6d). 
	This, I think, suffices to show that Spinozistic modes cannot be shared by two substances. Now comes the question whether two Spinozistic modes - such as Geppetto and Pinocchio – can share a mode of a mode. On the face of it, it seems that if some inherence relations allow for their modes to inhere in two substrata, and other inherence relations do not allow it, we would have a brute bifurcation of inherence, a bifurcation which Della Rocca must reject. But Della Rocca may argue that this bifurcation is not brute, since it is only in the case of substrata that are substances that the substrata cannot causally interact. Substrata that are not substances may interact causally, and therefore may, perhaps, share a mode (of a mode). 
	Still, I do not think Spinoza could allow for such a case. Were table T a genuine property (or mode) of both Geppetto and Pinocchio, it would have to be either a universal or a particular property. T is clearly not a particular property since it is allegedly a property shared by two things, but it also cannot be a universal since Spinoza clearly and strictly rejects the reality of universals (E2p40s1). The table might be the joint effect of Geppetto and Pinocchio, but it cannot be their shared property.

	3. Spinoza’s Dualism

	At this point, I would like to start outlining an alternative to Della Rocca’s view. As I pointed out at the beginning of this paper, Della Rocca does have powerful arguments to support his position, and it is an essential condition of any attempt to present an alternative reading to his that it should be able to rebut these arguments.
	One alternative that I believe is not likely to work is to reject the causation-conceivability biconditional (3). Let’s first consider the prima facie appeal of this venue. The major text that supports the causation-conception biconditional is E1a4, and in almost all cases Spinoza uses it in only one direction, i.e., from causality to conception (which leaves open the possibility of conception that is not accompanied by causality). The only exception - where Spinoza does derive causality from conception - is E1p25d, and it is not impossible that this could have been just a slip of pen or simple error. 
	I tend to think that this alternative is not very viable for the following reason. The only case in which we find Spinoza suggesting a conception relation that is apparently unaccompanied by causality is that of inherence; he holds that what inheres in something else must also be conceived through that thing. But since inherence itself is always accompanied by causation, it seems that, in one way or another, causation always accompanies conception. Hence, I believe, we should affirm the causation-conception biconditional.
	So what, then, is the alternative? Let us go back to three of the formulae we have examined before:
(3) x is the cause of y, iff y is conceived through x (Causation-Conception Biconditional)
(4) x is in y, iff x is caused by y (Inherence-Causation Biconditional).
(5) x is in y, iff x is conceived through y (Inherence-Conception Biconditional).	
	I suggest that Spinoza accepted (3), and only the left-to-right direction of both (4) and (5). In other words, instead of (4) and (5), he accepted
(6) If x is in y, y causes x (Inherence Implying Causation Doctrine), and
(7) If x is in y, x is conceived through y (Inherence Implying Conception Doctrine). 	Arguably, in Spinoza there is a genuine bifurcation between two kinds of causation as well as between two kinds of conception, but neither bifurcation is a brute fact, and it is to the reasons for these bifurcations that we now finally turn.
	Spinoza’s important distinction between immanent and transitive causation has already been discussed above. Immanent causation involves inherence of the effect in the cause, while transitive causation does not. Since, as I believe, the relations of causation and conception perfectly reflect each other, the bifurcation of causation should be mirrored by a bifurcation of conception. Indeed, I believe that we have strong textual support for that conclusion.
	Consider the following passage from Spinoza’s Short Treatise. The context of the discussion is a distinction Spinoza draws between two kinds of definition. The first kind includes definitions “of attributes, which are of a self-existing being,” while to the second belong definitions
[o]f those things which do not exist through themselves, but only through the attributes of which they are modes, and through which, as [als] their genus, they must be understood. (KV I, vii| I/47/4)
Modes are conceived or understood through their attributes, which function as their genus; but obviously my parents, or any of my other transitive causes, are not in any sense my genera, nor does it make sense to say that the carpenter is the genus under which the table falls. While the table is conceived both through the carpenter and through the attribute of extension (both are in some sense the cause of the table), there is a significant difference between these two kinds of conception. Extension explains the table by being its genus, while the carpenter explains the table in a completely different manner. This issue deserves careful and detailed discussion that goes beyond the scope of this article, but to put things briefly, the distinction between the two kinds of conception seems to be a distinction between the explanation, or conception, of essence, as opposed to the explanation of existence. The carpenter (i.e., God qua the carpenter) explains the existence of the table, while Extension (i.e., God qua Extension) explains the essence of the table. Consider the following passage from E1p17s: 
A man is a cause of the existence of another man, but not of his essence, for the latter is an eternal truth. Hence, they can agree entirely according to their essence. But in existence they must differ”(II/63/18)
Here Spinoza is saying that the causes of the essence and existence of a finite thing are distinct. But if the causes are distinct, then, following E1a4, the conceptions or explanations, of the essence and existence of a finite thing should also be distinct. Essences of finite things are conceived and explained through their attribute, while the existence of a finite thing is explained through another finite thing (E1p28d).
	One may, of course, say that the Short Treatise is an odd and early text and that therefore we cannot take as conclusive evidence this distinction between conception that does and does not involve falling under a genus; yet a very similar distinction appears in the Ethics itself. Spinoza uses concipire (to conceive) very frequently in the Ethics. There are two important features of Spinoza’s use of this term which I would like to point out here. First, in many places in the Ethics (and in other texts), Spinoza talks about modes being conceived under [sub] an attribute, but he never claims (nor does it make sense to claim) that an effect of a transitive cause is conceived under that cause. Consider, for example, E3p2s:
[T]he Mind and the Body are one and the same thing, which is conceived now under the attribute of Thought, now under the attribute of Extension [Mens, et Corpus una, eademque res sit, quae jam sub Cogitationis, jam sub Extensionis attributo concipitur](II/141/25).
The table is conceived ‘under’ Extension, but it is definitely not conceived ‘under’ the carpenter. To be ‘conceived under’ is quite close to the Short Treatise’s view of the attributes as the genera of modes. 
	Second, if we look carefully at Spinoza’s use of concipere in the Ethics, we will find that he never uses it to designate the conception of a mode through its transitive cause. A mode is said to be ‘conceived through’ God’s essence or the mode’s nature, but, as far as I can see, never through another mode. Given Spinoza’s abundant use of the term, it is highly unlikely to be a coincidence. Based on this finding, one could argue that there is no conception relation between ideas of modes which are connected by transitive causation, but I believe that this is not the case. At the beginning of this paper we called the relation designated by E1a4 (“The cognition of an effect depends on and involves the cognition of its cause”) a relation of ‘conception’. This was in agreement with the common use in contemporary Spinoza scholarship, though it might have been slightly misleading, since concipere does not appear in E1a4. I do think that E1a4 indicates a certain relation we would call a conceptual relation, since it is a relation between ideas or concepts. Spinoza’s use of E1a4 seems to show that this conceptual relation holds between ideas whose objects are connected by immanent causation, as well as transitive causation. Hence, while both immanent and transitive causation are mirrored by conceptual relations, Spinoza seems to reserve the verb concipere to a particular kind of conception, the conception of things (or their properties) either through the essence of God or through their own essence. In both cases, concipere is tied with the explanation of essences and mirrors only immanent causation. 
	We have thus two parallel bifurcations: a bifurcation of causation into (A) immanent and (B) transitive causation, and a bifurcation of conception into (A`) conceiving things through (or under) God’s essence or their own essence (‘concipere’), and (B`) the conceptual relation between an idea and its external cause which explains the existence but not the essence of finite things. These two bifurcations also seem to map well onto other bifurcations we have already encountered: (1) between causation that is, and is not, in time, and (2) between causes which are more real than their effects, and causes which are as real as their effects. An effect of an immanent cause is not posterior in time to the cause and is less real than the cause, while an effect of a transitive cause is equally real, and is posterior in time to the cause.
	What we have done so far shows that we can explain the bifurcation of conception through the bifurcation of causality (or the other way around). Still, the question remains whether we can go even deeper and explain the bifurcation of causality. Yes, we can.
	When Spinoza discusses the adequate definitions of things, he splits the discussion and suggests that things which exist through themselves should be defined differently from things which do not exist through themselves. This essential bifurcation between two kinds of things is restated by Spinoza in numerous ways. Some things are free [libera], while others are compelled [coacta] (E1d7). Some things “are called necessary by reason of [their] nature,” while others are necessary by reason of their cause (E1p33s1). Some things exist (or do not exist) by reason of their essence, while others “by reason of the whole nature” (E1p11d). All these bifurcations amount to Spinoza’s central division between substance and mode. Only the substance exists and is necessary by virtue of its essence, and only the substance is free. Modes are never (fully) free, and they exist and are necessitated by virtue of causes that are not their essence. While modes can strive to be more free and independent, they will never be substances.
	The distinction between substance and modes is also related to another crucial distinction of Spinoza, that between Eternity and Duration.
The difference between Eternity and Duration arises from this. For it is only of Modes that we can explain the existence by Duration. But [we can explain the existence] of Substance by Eternity, i.e., the infinite enjoyment of existing, or (in bad Latin) of being (Letter 12| IV/54-55).
I am not sure whether Spinoza later changed his mind or not, but at least in this letter, Spinoza seems to conceive of eternity as the existence of substance and duration as the existence of modes. Of course, modes, insofar as they are modes of the substance, can in some way participate in the eternity of substance, and I assume that this is what Spinoza means by saying that modes can be conceived sub specie aeternitatis (E5p29d). 
	Let me here stress two points. First, the bifurcation of substance and mode is not one in which the two sides are completely alien to each other (as with Kantian intuitions and concepts). The modes are modes of the substance, yet they have essential characteristics which are strictly opposed to those of substance, and it is this opposition between substance and modes, or natura naturans and natura naturata (E1p29s), that ultimately grounds the bifurcations of causation and conception.
	Second, according to Della Rocca, the PSR does not allow for the existence of brute or illegitimate bifurcation, but at times it seems as if Della Rocca is arguing for an even stronger thesis, i.e., that for Spinoza all bifurcations are illegitimate. Della Rocca claims that Spinoza’s naturalism (which itself is motivated by, or even tantamount, to the PSR) “is the view that there are no illegitimate bifurcations in reality,”  but the question is whether there are legitimate bifurcations in reality. To my mind, the passage just cited from Letter 12 shows clearly that at the center of Spinoza’s metaphysics there is a sharp division between the existence of substance (eternity) and the existence of modes (duration). Della Rocca defines the naturalism he ascribes to Spinoza as the “thesis that everything in the world plays by the same rules,” but playing according to the same rules does not mean that there is only one single player. In other words, claiming that the nature of substance is different from the nature of modes is consistent with the strict commitment of both to the same set of rules.
	I have argued elsewhere that, for Spinoza, modes are nothing but the propria of God which follow necessarily from God’s essence. Spinoza understands the relation between an essence and its propria as one of immanent causation, in which case the propria are simultaneous with their cause, and inhere in their cause. The causation between finite modes is transitive causation. The picture we get is that both causation and conception are bifurcated, but neither bifurcation is a brute fact. The bifurcation of conception is grounded in the bifurcation of causation (or the other way around), which is ultimately grounded in the bifurcation of existing things into natura naturans and nartura naturata, eternity and duration.
	But how about this very last bifurcation? Is the substance-mode bifurcation brute? If so, one may invoke the PSR in order to obliterate it by denying the reality of duration and modes and embracing the acosmist interpretation of Spinoza, which affirms the sole reality of undifferentiated natura naturans. One can now see why Hegel claims that “ex nihilo nihil fit,” a variant of the PSR, leads to acosmism, but in spite of the charm and boldness of this interpretation, I do not think that it is sustainable. Assuming that the acosmist interpretation of Spinoza is wrong, we may, and indeed should, ask: Why is it the case, for Spinoza, that there is a universe of finite modes and not just one eternal and undifferentiated substance?  Why does natura naturata follow from natura naturans? Why are plurality and duration real?
	
	4. Conclusion
	Della Rocca’s bold and remarkable thesis led us to one of the deepest questions in Spinoza’s metaphysics. I have argued in this paper that Spinoza never actually identified the relations of inherence and causation, and that any attempt to suggest such an identification as a friendly amendment to the system is inconsistent with some of Spinoza’s main theses. I have provided several arguments in support of the latter claim. In the last part of the paper, I have argued that in Spinoza there is sharp bifurcation between two kinds of causality as well as between two kinds of conception, and that both bifurcations are grounded in the bifurcation of existence into substance and modes. At this point we may legitimately ask as to the reason for this very last bifurcation: Why does God have modes?
	This last question seems to press Spinoza from different directions. On the one hand, Spinoza’s strict commitment to the Principle of Sufficient Reason demands that this question be answerable. Spinoza cannot avail himself of the claim that God created the world by virtue of some arbitrary grace. On the other hand, it seems that one cannot say that natura naturans needs or demands the existence of natura naturata, since this would presumably invert the dependence relation of modes on the substance.
	This deep and foundational question requires a thorough investigation and hence must wait for another occasion, but let me here just hint at an answer. The very definition and essence of God – “By God I understand a being absolutely infinite” - asserts the reality of an infinitely infinite multitude.