My discussions so far support the malfunctional belief hypothesis, according to which delusions are malfunctional beliefs. This hypothesis has two major sub-hypotheses: (1) delusions are beliefs, and (2) delusions are malfunctional. Sub-hypothesis 1 was defended in Chapter 2; delusions are produced and consumed by the cognitive mechanisms with the right kind of functions in an attempt to perform the right kind of functions (the doxastic mechanism hypothesis 2). Sub-hypothesis 2 was defended in Chapter 3; some of these cognitive mechanisms (and other mechanisms that are indirectly relevant) are malfunctioning or, in other words, failing to perform their functions due to intrinsic problems (the malfunction thesis). In defending these sub-hypotheses, I made some assumptions (in particular, empiricist assumptions) about the process of delusion formation. The aim of this chapter is to make these assumptions explicit and articulate my commitments to the process of delusion formation. This is, in effect, to answer the etiology question.