Why Surrealism is Art

Surrealism is logic as an art form.

Art is produced as elements are arranged following and, in many cases, not following, certain contextual rules. 

When someone tries to create surrealism without logic, it ends up as what we call randomness.  Surrealism is rather deliberate violations of logic in ways to create a caricature, or an "artistic depiction", of logic itself.  Surrealism is painted logic. Without a logical semblance holding it together, it would lose its dreamlike quality.  That a surreal scene appears to almost represent reality is what makes it surreal at all.

That the categories and objects blend and mesh is important to surrealism, and there is a structure to blending concepts that way.  Otherwise, it would just be unexpected.

There's lots of forms of surrealism; its style is particularly suited to the horror genre, but it also finds a good home in satire and, lately, memes. I prefer surrealism with a more "nostalgic" feel, but no matter the medium, the elements are the same: real concepts are welded in unexpected ways, but always with enough real logic to create a harmony, rather than a discord.

Surrealism can, however, go the other direction: too much logic, and it instead becomes a message.  No longer dreamlike, it now has a specific and easily understood meaning.  Most political cartoons are an example of this; rather than real concepts being juxtaposed in the specific logical gaps and seams, real contexts are juxtaposed along clear logical lines, creating what we call symbols.  This doesn't preclude people assigning meanings to surrealism, just that a surrealist piece does not require the meaning- it isn't inherent.