Grerat optical illusion book!

The human being is a sponge who absorbs the changes of the physical world surrounding him. Actually, if the physical world had been unchanging, we wouldn’t need to receive sensations on the world that surrounds us since all would be static and everything would definitely have its final place!
Our sense organs continuously check, then, the changes of our immediate environment to allow us to act and react in keeping with it. If we see a wall in front of us, for example, we won’t charge into it, of course, but try to avoid it! Our senses however detect only a part of the reality – the most useful for us -  and translate it in an ‘analogical’ way. Yes, our senses work analogically... For instance, it’s difficult to consider a single color in a distinct way, but always in relation to others. The same red color will be perceived differently according to the content or the context where it lies within.