Recently, similarity theories have gained popularity as empiricist epistemologies of non-actual possibilities. Such theories suggest that one gains justification for the belief that this glass could break because one knows (or has a justified belief) that there is a relevantly similar glass that did break. Similarity theories rely on ordinary knowledge of actuality in order to explain our knowledge of non-actual possibilities. However, such theories run in to trouble when it comes to explaining issues related to the necessity of origins. In this paper, I will present the problem in detail and present a fully general solution that relies on the temporal order of the relevant similarity relation.