This is a paradox because the block in the right hand corner is drawn on top of the block that it is supposed to be behind. When you first look at the cube it seems like the block in the right hand corner is both where it should and shouldn't be. The closer you look you notice that it is positioned incorrectly, tricking your eyes into seeing 2 seemingly possible structures, but the structures you see can't both be true.
These are the materials needed to create invisible ink. Invisible ink is an oxymoron. The whole point of ink is to write out something that can be read. Invisible ink cannot be read, because it's invisible. The 2 terms are contradictory, ink being something you can see while invisibility is, well, invisible. They are put together to create a new idea/invention, but the words used have opposite purposes.
This is another paradox. There are stairs that seem to be going down because one side of the structure gives it the appearance of having height. But from the other sides the platform looks like it's at an even height, which makes it impossible for the stairs to be leading downwards if the whole platform is equal. At first glance it seems as if the man will eventually walk down the stairs, but when you study the structure you find that this is impossible.
