 Timaeus speaks about the Demiurge’s practical reasoning for creating the cosmos as he did. No cosmologist can deduce these reasons from various premises commonly accepted. He has to imagine them, but they are neither fantastical, nor sophistic. The cosmologist exercises his imagination under some constraints. He has to come up with reasonable and coherent conjectures. And in good Socratic and Platonic tradition, he has to test them with others. This is what Timaeus does. He expounds his cosmology in front of other philosophers, whom he calls kritai, “judges” (29d1). They are highly skilled and experienced philosophers: Socrates, Critias and Hermocrates and at the beginning of the Critias, the sequel to the Timaeus, they express their admiration for Timaeus’ cosmological account (107a). One may say that Timaeus’ account has been peer-reviewed. The judges, however, says Plato, have to be tolerant, for in this field one cannot provide more than conjectures. Timaeus’ cosmological discourse is not aimed at persuading a less philosophically inclined audience to change their lives. It may be argued that its creationist scenario was meant to make the difficult topic of the genesis of the realm of becoming more accessible. In the Philebus, in a tight dialectical conversation, the genesis of the realm of becoming is explained in abstract terms (the unlimited, limit, being that is mixed and generated out of those two; and the cause of this mixture and generation, 27b–c). But the Timaeus aims at encompassing more than the Philebus. It aims not only at revealing the ultimate ontological principles (accessible to human reason, cf. 53d), and at explaining how their interaction brings forth the world of becoming, but also at disclosing, within a teleological framework, the reasons for which the cosmos was created the way it is. These reasons are to be imagined because imagination has to fill in the gaps that reason leaves in this attempt to disclose the reasons for which the cosmos was created the way it is.