This article outlines an epistemological perspective to understand the organism as a temporally changing whole. To analyze the mental faculties involved, the organism’s development and persisting existence is differentiated into four interdependent aspects: descent, future existence, persistent species, and environmentally adapted physical appearance. It is outlined that these aspects are recognized by comparative memory, concept-guided anticipation, conceptual thinking, and sensory perception, respectively. Furthermore, it is pointed out that these aspects correspond to the famous four Aristotelian “causes” or principles of explanation. (...) The descent of an organism corresponds to Aristotle’s efficient principle (“where does it come from?”), its future existence to the final principle (“what is if for?”), its physical structure to the material principle (“out of what is it?”) and its persistent species to the formal principle (“what is it?”). Aristotle regarded the unity of the efficient, formal and final principle as the ontological cause of the organism and called it the “soul” (psyche), while the material principle can be understood to represent its “body” (soma). I suggest that Aristotle’s “soul” corresponds to three of the four mental faculties required for cognition of a self-maintaining organism. I argue that in a Kantian perspective, the Aristotelian “soul” represents the condition for recognizing an organism at all. Therefore, the Aristotelian principle of life becomes intelligible and even empirically observable through the inner sense. In summary, I suggest that the four aspects of the organism described here can be viewed as the general, epistemological and ontological principle of the organism, the Bio-Logos. (shrink)