“Conception” has to do with the creation of Gatsby’sself; Gatsby is a self-made man financially. Some other details are: his appearance,reputation, and mysteriousness; most importantly, his love for Daisy and thereminiscence of their brief little love affair. “Platonic” comes from its nounform Platonism which means ‘the philosophy of Plato stressing especially thatactual things are copies of transcendent ideas and these ideas are the objectsof true knowledge apprehended by reminiscence’ (Merriam Webster). Plato believed the world we see was an illusionof some idea or object that is beyond what we humans can see or comprehend. Gatsby’sidentity was created from his platonic view of himself: his view that his lovefor Daisy was transcendent, it was beyond the normal, and it trumped the usualhuman limits. He made himself, his reputation and image to win Daisy’s heartback, believing their love was something pure and special.
However, he was wrongabout Daisy’s love for him, which tying back into the beginning of the novel, shewas the “foul dust” at the death of his dream.