In The Guide to the Perplexed III.37, Moses Maimonides attacks pagan ‘medical’ practices which give a sheen of efficacy but are ultimately dependent on magic and astrology. Nonetheless, he allows certain exceptions found in late antique rabbinic literature which have been proven through experience – even if they are not ‘prescribed by reason’. His preference for empiricism over principles or causes is noteworthy. In this, Maimonides follows others such as al-Ghazālī who prized Galen’s medical empiricism over medical theory. In this chapter I examine these exceptional cases in light of the literature of antiquity in order to discuss their efficacy. I also reveal how Maimonides’ begrudging acceptance of experience over theory also underpins his ‘proof’ of the creation of the world – which also ultimately turns to Galen. Thus, I reflect on the importance of Maimonides’ loyalty to Galen’s experimental method for both physics and metaphysics, showing methodological continuities across different domains.