In other dialogues, the "Sophist", "Statesman", "Republic", and the "Parmenides", Plato himself associates knowledge with the apprehension of unchanging Forms and their relationships to one another (which he calls "expertise" in Dialectic), including through the processes of "collection" and "division". More explicitly, Plato himself argues in the "Timaeus" that knowledge is always proportionate to the realm from which it is gained. In other words, if one derives one's account of something experientially, because the world of sense is in flux, the views therein attained will be mere opinions. And opinions are characterized by a lack of necessity and stability. On the other hand, if one derives one's account of something by way of the non-sensible forms, because these forms are unchanging, so too is the account derived from them. That apprehension of forms is required for knowledge may be taken to cohere with Plato's theory in the "Theaetetus" and "Meno". Indeed, the apprehension of Forms may be at the base of the "account" required for justification, in that it offers foundational knowledge which itself needs no account, thereby avoiding an infinite regression.