Can we trust our perceptions?

 A classic problem with ancient (Greek) philosophy was the untrustabilty of direct experiences of the world around us.  There were many, many ways in which our perceptions seem to fool us into thinking what we see is real, when it is not.  Classically, the optical illusion of a stick in a glass of water comes to mind.  The refraction of the water makes the stick appear to have a bend at the point it enters the water, when it clearly does not if it is pulled out.  Another is that drinking wine makes the floor tip left and right, making walking difficult.  Heat waves make the distance look like it is wet, when it is not.  That sort of thing.

Empiricists believe that the world can be known from direct experience.  "Just look around", they say, "and see the world as it really is!"   Can we look at a sunset and understand what we are seeing without understanding about light's interaction with atmospheric particles and low angle refraction?  Can we see a human birth and understand all the biologic and physiological phenomena at work, all at once?  Experience gives us access to certain sorts of phenomenon, but at a sort of macro level, at least historically.  Science helps us to see progressively small things, aiding this perspective, but still, it all ends up as people seeing things they can understand and observe directly.

Rationalists say that they can know things just by thinking about them.  Certain logical and mathematical concepts are true because they must be true if the world conforms to the logical necessities of math and logic.  We don't need experience to know that 2+2=4.  Or that cause and effect are real.  Physicists seem to spend a lot of their energy in working out that certain cosmological phenomena must be this way or that, based on what we know of the fundamental principles of matter and energy.  Observation is so frustratingly difficult in these galactic spaces that logical evaluation is a much better course of action.  

Where has direct experience of the world around you failed you?  Can you say you can really trust your senses?  Is logic a better basis of understanding in some cases?  Come prepared to discuss these and other examples of your interaction with the world around you, and how you have been fooled from time to time.