What Are Mental Phenomena?

Brentano famously defined psychology as the study of mental phenomena. But what are mental phenomena? In this paper I argue that mental phenomena are mental ‘appearances', where an ‘appearance' is neither a mere semblance nor some object that appears. Instead, just as physical appearances are ways things appear to me (something that is routinely captured in perceptual reports such as 'this cup appears *red* to me'), mental appearances are ways I appear to myself, for example as *perceiving a red cup* or *desiring an espresso*. I provide textual evidence for this interpretation before exploring some of its implications for a correct understanding of Brentano’s descriptive psychology and intentionality thesis. It follows, among other things, that intentionality is neither a relation nor a monadic property of mental states but rather a specification of the way mentally active subjects appear to themselves.