Is atheism rational?

whereas mystics dream up non-existent principles out of their non-thinking.

You left out that they bully and hoodwink others into accepting said principles on blind faith; which is the point of mysticism.

The dictionaries is full of definitions. The American Heritage is my usual choice. I chose definition #3, the first which fits most Gods that people tend to discuss, such as the Christian God or the god of the seas Poseidon: “A being of supernatural powers or attributes, believed in and worshiped by a people, especially a male deity thought to control some part of nature or reality.”

As far as I can tell, no part of that definition conflicts with any of what you’ve written.

I would also disagree with “One out of many”. It’s highly probably the being we just defined is non-existant and there’s a slim possibility it’s unique.

Since we just defined God that doesn’t apply.

“A being of supernatural powers or attributes, believed in and worshiped by a people, especially a male deity thought to control some part of nature or reality.”

This is not a definition but description of arbitrary concept. Definition is what separates species from the rest members of the genus by it essential property. There is no such a thing as a genus of supernatural. Supernatural means that something exists without to be part of existence, which is contradiction in terms. Whatever is not part of existence cannot have any properties and therefore cannot be defined. Even descriptive definition applicable only to existent objects, not to fantasies. Only objects or relationships could be defined. If God is defined than he is an object with certain properties which separate him from all other objects. He is therefore limited, part of existence and thus, not God.

While I don’t accept your particular example of something which at the time had no evidence for it (flying was shown to be mechanically possible by many organisms, including birds and insects), it is true that sometimes beliefs which have no evidence for them later turn out to be true. This does not refute or in any way weaken the argument that Ayn Rand was making. Until some evidence is presented, there is no systematic way of separating these types of claims from any other random claim (e.g. the Flying Spaghetti Monster). Evidence is the only basis on which to separate one claim from another. Any claim for which there is absolutely no evidence must be regarded as arbitrary. An attempt to live consistently by any other policy leads to madness, and any attempt to live generally by this policy but make exceptions for whatever you want is equivalent to throwing out epistemological rules altogether.

Not only that, but someone actually beat him to it. I believe there was an Islamic aviator in the Arabian Golden age

would do you make of this description of an agnostic:

An agnostic doesn’t simply “not know”. An agnostic can also believe that there *is* no knowing - that there might be something, but if there is, it’s of a form that is unknowable. I, for instance, believe that there *may* be some force out there, but I *firmly* believe that no human can possibly have the slightest idea of how to conceptualize it or affect it or know how to communicate with it, yet I still place myself among the ranks of agnostics. This is not an issue of knowing or not knowing (that is, “being sure”). This is an issue of believing that whatever is out there is unknowable, even were it to present itself. It’s a difference between certitude and understanding. It’s like the difference between not having a powerful enough microscope and the Heisenberg uncertainty principle. If you don’t have a microscope powerful enough, you won’t know what an electron looks like. However, Heisenberg goes farther, in that he asserted that you can’t *ever* know. It is intrinsically unknowable, so there’s no point in speculation.

I’ve been an agnostic before I came to understand that acknowledging the possibility for which no evidence (not even theoretical evidence) exists is like saying, “Well you can’t prove that unicorns aren’t real magical creatures, so they MIGHT exist.”