Phantasy comes from light, φῶς, its etymological root. Those things that appear in light, φαίνεσθαι, that, in other words, are projected in and by it, figured and disfigured by it, split in two ways. First, there are those things that are comprehensible, legible, and ordered in a consciousness (those things that appear according to a logos), which end up in the méconnaissances of phenomenology. What does not submit to discourse and understanding, however, what precedes, lacks, or exceeds its logic, merely appears as phantasy.
This doesn’t clarify much, except perhaps a certain obscurity, which is why phantasy is such a difficult concept—that is, if one can grasp it in a concept at all. Nonetheless, for psychoanalysis, phantasy is as important as it is hard to define. The idea of phantasy was in fact so contentious that, in 1940’s London, an entirely psychoanalytic school of thought had to be created in part just to account for its consequences. And although it is no longer considered to be a particularly controversial issue, there is still no consensus on the exact role of phantasy in psychoanalytic theory. Thus here, far from saying anything definitive, I will merely attempt to trace one particular lineage of the ‘concept’ of phantasy through its development in (Sigmund) Freud and its interpretation and modification (becoming “unconscious phantasy”) by Melanie Klein and Susan Isaacs.