This chapter sets out the formal case for a proposal that underpins the argument of this book; that there are two axes of explanation in psychology. One has to do with the field of synchronic relations. The other has to do with the genesis of events over time ‘diachronically’. The idea that the past explains the present is fundamental in modern-day psychology. But we commit a fallacy if we assume this to be the only or the primary dimension for psychological (or any scientific) inquiry. This fallacy has long been known to philosophers as the genetic fallacy – the word ‘genetic’ being used here to mean ‘pertaining to genesis’ (unfolding over time), not just to what we now call genes (the functional units of DNA that all living beings carry on their chromosomes). According to my argument, and to philosophers of the genetic fallacy, the primary question in understanding any entity is an atemporal, synchronic one: ‘what is X?’.