Fidelity to the Cartesian philosophy requires a defense of dualism as well as mind-body union and interaction, all the while keeping to some form of the causal likeness principle. Each of these positions are ones that Descartes maintained throughout his writings. Yet, successors and scholars alike have noted the inconsistencies that arise from defending these views conjointly and have argued that one or more of them should be abandoned. Even the first generation of Cartesian successors whose fidelity to the Cartesian (...) principles was especially steadfast, such as Louis de la Forge, have been interpreted and characterized as giving up causal interactionism and wittingly or unwittingly embracing occasionalism. In my dissertation project, I have made mind-body not body-body cases the starting point of the inquiry into cartesian causal interactionism and from there developed a general model of interaction. This goes against the scholarly norm of focusing on the body-body cases to develop a model that then cannot explain how the mind-body cases work. This is not a minor change in point of view, but rather, requires a paradigm shift in cartesian studies, particularly with respect to understanding mind-body union and interaction. Further supporting the needed paradigm shift in our reading of La Forge is that in his account of union criteria we discover that mind-body union is the true union and that body-body unions are considered such only by extension. As such the case of mind-body union should be taken as the exemplar case and not body-body. According to La Forge, mind and body are linked via the relative attribute of will and share a relationship of mutual and reciprocal dependence. Union is not based on a spatial relation. The union is a hybrid mode – a way of being of the two substances if and when they stand in such a relation to one another. While, the union provides the commonality needed to bridge the gap of what two distinct substances have in common it does not provide the explanation of how mind and body interact. Operationalizing the union in terms of mutual and reciprocal dependence requires further explanation. La Forge explains that mind and body are secondary causes. The causal model of interaction of mind and body is one in which these particular causes and their relation of mutual and reciprocal dependence allows for the action of the one to bring about the effect in the other. The body’s movements stimulate thoughts in the mind and the mind’s thoughts direct movements in the body. There is a bi-directional causal interaction. Furthermore, by coupling La Forge’s account of union and interaction with that of Nadler’s proposed occasional causation model we find that mind and body both have causal agency in the weaker secondary sense. Both substances have the power to determine and direct motion, albeit neither mind nor body create motion per se. La Forge establishes a key distinction between universal and particular causes, which then grounds his subsequent attribution of secondary causal power to wills – to direct the movements of bodies, and to bodies in virtue of their modes of configuration – to direct the movement of other bodies. While, God is the universal and efficient cause that creates minds, bodies, and motion, He has minimal involvement in the particular determinations of volitions and movements. He imparts power to His creatures to determine motion. God conserves the world and the laws set by Him in the form of three laws of motion and seven laws of union. However, finite substances such as mind and body also have force, albeit not in the same sense as God does as the universal and total cause, but rather as particular secondary causes that have autonomy and can determine the direction and local quantity of motion. Thus, La Forge explains how both mind-body and body-body interactions are genuine causes, i.e., non-occasionalistic. Accordingly, in keeping with Cartesian philosophy La Forge maintains dualism, and provides an account of union and an account of interaction that is not occasionalistic. Both mind-body and body-body interaction is based on equivocal causation – the effect does not strictly resemble the cause – but both operate through the likenesses of relations of union, mutual dependence and proximity respectively. Thus, La Forge’s causal model that has minds and bodies interacting based on their relation of mutual and reciprocal dependence, and bodies interacting based on their shared mutual proximity and dependence, provides a weaker account of the causal likeness principle. Nonetheless, there is nothing inconsistent with his defense of a weaker notion of likeness that does not demand resemblance. My examination of La Forge’s Treatise on the Human Mind has demonstrated that we can maintain fidelity in our interpretation of Descartes and the Cartesian philosophy that maintains its adherence to dualism while giving an account of union and causal interaction. (shrink)