Summary of doctoral thesis: My thesis examines the issue of cognition in Plato’s Timaeus, and focusses on Timaeus’ discussion of two cases occupying opposite ends of a spectrum: the cognitive activity of an immortal rational soul in the best possible condition and that of an immortal rational soul in the worst possible condition. The first is the cognitive activity of the World Soul, described at Ti. 37a2-c5, which forms the basis of my first chapter. The second is the cognitive activity of a human rational soul that has just been embodied, described at Ti. 42e5-44c4, which I tackle in chapters 2 and 3. In chapter 2, I argue that the human type of immortal rational soul is first embodied in what is best understood as an embryo. In light of this hypothesis, I analyze, in chapter 3, the initial disruption of its cognition. I then draw a comparison between the kinds of cognition of the kosmos and that of an embryo. On the basis of this comparison, I discuss the first steps of the cognitive recovery that takes place when the embryo develops into a child. This discussion in turn paves the way for understanding the relationship between cosmic and adult human cognition, and in particular, how the former can be a model for the latter.