If all mental process are physical in nature and we make a philosophical experiment about somebody who has complete knowledge of all physical processes, we do not reach a contradiction about him not being able to "truly know" what certain feelings are... because in that case he should be able (by hypothesis of "complete knowledge of all physical processes") to simulate such feelings in mental processes within a virtual world in his own imagination.
tialoc, I apologise for angering you. I'd hate for you to feel that I am being confrontational and hope you can accept my apology.
I think we need to reach a consensus first of all on what it means to have knowledge of a physical process. To me, at least, a physical process is only known through bare difference. As an example, we can think of the parameter spin of elementary particles. We do not know what spin is in and of itself but we do know that spin values change from one particle to another - it is either 1/2 or 1 (and the same in negative values). However, knowing the bare difference between values of spin on different particles gives us no clue about what spin is itself - all we know is its quantity.
Now, we can make one of two observations. First of all, we can say that we know everything there is to know about the physics invloved because we can accurately measure quantum experiments (employing spin values) upto ten decimal places. The physical process is completely known but I don't think it's possible to simulate the idea of spin in one's mind through just knowing it's quantitative value. Certainly I have no idea what the sensation of 1/2-spin on an electron will feel like to simulate but I am not the final authority of course.
Secondly, we could say that there is nothing more to spin but its quantitative value. It has no appearance or sound or feel - it just is a quantity.
In both cases, however, I don't see how knowing the full physical value of something has helped us know the experience of it. In the first case we cannot extrapolate to the quality of an object from its quantity and in the second we agree that the quantity has no qualitatitve content and thus is useless in explaining sensations anyway.
I would state and perhaps this is where we are disagreeing, that there is nothing more to knowing about something physically than knowing its quantitative value - the parameters that physical explanations work within don't allow any intrinsic value or sensation. Another instance is that of colour. We know that red has a certain wavelength and that it is an electromagnetic wave and that it travels at the speed of light. Now, knowing the wavelength and its speed and its fequency is only knowing about bare differences in quantitative value. Can somebody who has never seen red really know the sensation of red by knowing that it has a different wavelength to blue? Does that give us enough knowledge of red to "simulate" the colour?
I would, I'm afraid, have to say no to that. If we were to add the sensation of red into the full physical description of red then it is no longer a physical description.
You also made an interesting point about whether love itself is a mental or physical process. To this, I think all we can say is that we are concerned with the sensation of love perhaps not love itself. The question about knowledge of love is limited to knowing the experience of it from the physical parameters of quantitative values in bare difference from one another without any content of value whatsoever.
Topic: Love