Ad hoc concepts feature prominently in lexical pragmatics. A speaker can use a word or phrase to communicate an ad hoc concept that is different from the lexically encoded concept and the hearer can construct the intended ad hoc concept pragmatically during utterance comprehension. I argue that some philosophical concepts have origins as ad hoc concepts, and such concepts pose a challenge for experimental philosophy regarding these concepts. To illustrate this, I consider philosophers’ ‘what-it’s-like’-concepts and experimental philosophy of consciousness.