"Metaphysics is not recognized as a branch of philosophy in Ancient Greece, and Sextus Empiricus is not an exception in this sense; indeed, his attack on dogmatic philosophy is launched from the perspective of the traditional tripartition of philosophy into logic, physics and ethics. However, several parts of Sextus’ work deal with matters that we would count as metaphysical, in particular the passages where he discusses the dogmatic conceptions of the principles of sciences, of parts and whole, and of time and space. In all these passages, the background of Sextus’ attack is provided by claims of Plato and Aristotle, a fact all the more remarkable if one considers that when it came to attacking dogmatic Logic, Physics and Ethics the Stoics were mostly his privileged target. On the dogmatic side, the Platonists and Aristotelians of the Imperial period discussed the metaphysical subjects attacked by Sextus. Thus, it is worth reading Sextus’ attack in the light of Imperial Platonism and Aristotelianism. Yet this line of inquiry has been little pursued. My project ‘Scepticism, metaphysics and sciences’ aims to deepen our understanding of the connection between Scepticism and metaphysics at the beginning of the common era by dealing with the three topics I mentioned above: the principles of sciences, parts and wholes, space and time. The first part of my research will analyse the dialectic between Aristotle and his disciple Alexander of Aphrodisias on the one hand, and Sextus on the other, in relation to the crucial question on the existence of the principles of sciences and the possibility of knowing them. The second part will deal with the debate opposing Sextus to his Platonist rivals on the notions of parts and whole. Finally, the third part will provide a comparative analysis of the attack launched by Sextus on the dogmatic notions of space and time and of the relevant Peripatetic texts."