Irrational in Surrealism
The Surrealists thought that Western society placed too much emphasis on rationality. The problem with rationality, according to them, is that there is a whole realm of experience that exists outside of the rational mind. After all, we often behave in irrational ways, don't we? We might argue with our boyfriend or girlfriend about something silly, even if we know that that isn't the right (or the rational) thing to do. We might eat a lot of junk food, even if we know rationally that junk food isn't good for us.
The Surrealists felt that the irrational is a big part of our identity as human beings, and it's also a big part of how we understand and see the world. And they wanted their literature to reflect that. A lot of crazy things happen in Surrealist literature. A man might suddenly turn into a bird. A child might become a stone. The events and images that we'll find in Surrealist literature often don't conform to the laws of rationality. Anti-rationalism, and the irrational, are huge in this literature.
Chew On This
Gregor Samsa, the protagonist of Franz Kafka's The Metamorphosis, wakes up one morning to find himself transformed into a gigantic bug. This is just one of many examples of irrational events we'll find in Surrealist literature. Have a look at these quotations from the novella.
In Antonin Artaud's poem "Plates of Sound," brains brew in glass and the sky seethes with immodesties. Pretty irrational, we'd say. Have a look at the poem here.