 To think of FP as best explained by the use of subpersonal models assumes the existence of a set of structures targeting specific mentalistic elements—beliefs, desires, actions, emotions, and so forth. The Model TTist assumes that FP models can be elaborated in various ways to serve different purposes in different circumstances. FP models can be thought of as prediction devices: What will Fred do when he discovers the cafe is closed? Or a model might be used to arrive at FP explanations of action: Why did Fred go to the cafe? Or the  model might be elaborated upon to yield explanations seeking to detail both proximate and distal causes of behavior. Models also admit other kinds of elaboration. For example, a distinction between degrees of belief and desire might be introduced, and rationality constraints imposed.