What is the connection between these two theories in the Theaetetus?

Question

In the Theaetetus, one of the theories of knowledge examined by Socrates and Theaetetus is that all knowledge comes from perception. At the same time, they are examining another theory: that everything that exists is never still, immutable, but is constantly changing (becoming).

But they do not seem to make any distinction between the two theories. As I could understand, they lump them together, treating the two as the same hypothesis, only expressed in different ways. Or, perhaps, as parts of a single unified theory, which Socrates attributes to Protagoras.

To me, however, they look like very different theories, each one dealing with a different problem. I'm wondering what is the connection between them. A possible solution that occurred to me is: since everything can be perceived differently by different people – or even by the same the person at different times – nothing is absolute. Everything depends on the person perceiving it. But not in the relativistic sense that there is no truth. Let's take one of the examples given by Socrates. When a healthy man drinks wine, the wine tastes sweet to him, but when he is ill, it tastes bitter. It's not only the case that he perceives the taste of the wine differently, but the wine itself becomes different at the moment of perception. Is this the correct interpretation?

Answer 1

As I understand it, Theaetetus offers that 'knowledge is perception.' Socrates then adopts that assumption and explores the implication of such a world where knowledge is perception. In this world it follows that, as protagoras says, 'man is the measure of all things.' this is because man is doing the perceiving. It also follows that the world is never still and constantly changing because their perceptions last momentarily, the way we perceive a thing is constantly changing. So one theory (the latter - protagoras' theory) is an implication of the other theory (the former - knowledge is perception). The examples all describe/give insight to a world governed by the fact that knowledge is perception, ie. what we know is based on our perceptions.

In this world, you are right, nothing is absolute. An example Socrates uses to emphasize this point is the taste of wine when one is healthy as opposed to the taste when one is ill. The same wine taste differently, so we have a dilemma of deciding how the wine 'truly' tastes (is there a 'true' taste for that wine?). But in a world where knowledge is perception, we are always unerring. This is because everything is pragmatic. For example the wine tastes bitter for me. We don't contradict each other if the wine tastes different, because it tastes different for you.

From these examples and descriptions we anticipate many problems and innadequacies. But the discussions (subsequent theories and examples) are just implications of the definition 'knowledge is perception.'