  At 151d7–e3 Theaetetus proposes D1: “Knowledge is nothing other than perception” (aisthêsis). This proposal is immediately equated by Socrates with Protagoras’s thesis that “man is the measure of all things” (Hm for homomensura), which in turn entails the thesis that things are to any human just as they appear to that human (PS for phenomenal subjectivism). Socrates then adds that, in its turn, PS entails Heracleitus’ view that “All is flux,” that there are no stably existing objects with stably enduring qualities.