With that old/young lady thing I can see both but not at the same time but I dunno about the law of the excluded middle cause with the faces/goblet I can definitely see both at the same time.
The problem with the faces/goblet, in seeing both at the same time, is that you do not actually see them both at the same time. This is impossible. It is impossible because there is no goblet or faces ACTUALLY there. What is there is a simple pattern of black and white. The faces 'appear' to the viewer when the center of the image falls to the background, giving a false impression of three dimensionality in which the faces come forth to the viewer. Similarly, the goblet may come forth while that which surrounds it falls back. But it is ONLY through this process that either the faces or goblet appear at all.
So, when you believe that you see them both at the same time, what has occurred is a mental synthesis of each 'image' which has only come to you via an interactive process in the first place. In part, what this means is that if you look at the old lady/young lady enough, you will experience the same sense of "definitely [seeing] both at the same time."
This fact has been proven by 20th century Gestalt psychology, but it has been known by Buddhists for a very very long time:) The beauty of this is that you can understand it intellectually (as the psychological description provides) or you can, through mental training, see the whole process directly for yourself!
According to Buddhist psychology, we normal people are so caught up in the events of our lives, we have a great deal of difficulty ever seeing our own mental contribution to it (the process in which our mind actively imputes meaning/labels on things). One metaphor used to describe this is of a movie theatre. The movie in reality is composed of like 32 still images per second being flashed up on the screen - just as our mind experiences 65 frames/mental images per 'finger-snap' according to the Abhidharma. We would never guess this if we weren't told it were so. Further, we cannot confirm this (from our seat in the theatre) without being able to fine-tune the mind to see each of the 32 still frames for what they are - very difficult.
But the Buddhist texts say it is possible to tune the mind to actually see the frames as they occur - even though they are still occurring at 65/finger-snap. I believe this is possible from my own limited experience of watching the mind. While I still get caught up in the movement of the mind ALL THE TIME! - there are breaks where things seem to enter slow motion and I can observe a situation both as it occurs and as I cognize it - frame by frame.
Part of the practical implications that the Buddhists are going for developing ethical purity. Imagine an unmindful individual on a bus with some kids playing loudly while their father does nothing to restrain them. This unmindful person can very easily get angry, feeling his precious solace is unjustly violated, perhaps one of the children even bumps into him, so he is physically violated as well! Following this anger unmindfully, he may do any number of unskillful things. But if he catches his anger (a practice we all must develop over time) - sees that he is getting angry - see can seek to solve the situation skillfully. This situation is taken from Steven Covey's "The 7 Habits of Highly Successful People" and in it he suggests that the irritated person kindly ask the father to restrain his children. Thereupon the father apologizes and tells him that they are returning home fromthe hospital where the children's mother has just died. In this case, Covey suggests that the angry person's whole 'paradigm' is changed and anger is not even a possibility. This is a very useful thing to do, granted you can catch your anger - see it for what it is: an activity of your own mind.
Some people's philosophical disposition toward materialism forces them to say, 'no - there is something real out there that is making me angry,' refusing to see the activity of their own minds. If the materialistic view were correct than lashing out against whatever is out there is seen as one possibility while 'passively allowing others to violate me' is seen as the other possibility. Contrast this to the black/white views of the image above and you'll see how a person can 'get inside' one image (his own paradigm) so strongly that not only will the other image be seen as wrong, but the Truth of the Whole Image will be impossible to see.