By examining first-person descriptions of thought insertion I show that thought insertion is a complex and heterogeneous phenomenon. People experiencing this phenomenon have huge difficulty explaining what it is like due to the bizarre nature of the experience. Through careful analysis of first-person descriptions I identify some of the characteristics of thought insertion. I then briefly examine some of the philosophical literature regarding agency, ownership and thought insertion and conclude that the standard account of the basic characteristics of thought insertion (...) is inadequate when we consider the phenomenon as it is experienced. First person descriptions suggest that thought insertion is characterised by a lack of personal ownership and not simply by a loss of agency or authorship. This is an important factor that should inform research and therapeutic intervention. We cannot hope to arrive at appropriate therapeutic intervention or identify underlying neuronal mechanisms for the experience if we cannot say what the experience actually is. I further suggest that more analysis of first-person description is required for an improved account of the phenomenology of thought insertion. (shrink)