“Idealism is the philosophical term for the view that everything is ultimately mental in nature. It holds that nothing exists apart from minds and the ideas within those minds (hence idealism). Idealists believe that what we call material things, such as trees and tables, aren’t really objects that exist independently of our minds and our sensory experiences, despite what many people assume. According to the Idealist, trees and tables are only ideas in the minds. A tree is really just a tree idea or a tree experience. If there were no minds with ideas and experiences, there would be no trees, tables, or anything else. One influential Idealist, George Berkeley, put it this way: “To be is to be perceived.” In other words, nothing exists unless it is perceived by a mind.
Any Idealist doesn’t have to be an Atheist. Berkeley, for example, was a Theistic Idealist. He argued that there had to be a divine mind in addition to our human minds. But since you answered no to the God Question, you must be an Atheistic Idealist.
Atheistic Idealism isn’t nearly as popular today as Materialism, although many argue that it’s far more reasonable than Materialism precisely because it doesn’t ultimately deny the reality of our mental lives – including our reasoning! If reason is a feature of minds, only a worldview that affirms the reality of minds can be considered reasonable. So at least Atheistic Idealism has that advantage over Materialism.
Nevertheless, Atheistic Idealism faces some formidable difficulties. First, it seems very counterintuitive. Isn’t it a matter of common sense that trees and tables are real material objects that exist independently of our minds? If we can’t trust our common sense on that basic issue, how could we trust it on anything else?
What’s more, Atheistic Idealism seems to have the extraordinary implication that if every mind in the universe were destroyed, then the universe itself would cease to exist. It also implies that there has always existed at least one mind, because Idealism says that nothing exists independently of minds. So even at the big bang, there must have been one or more minds. But that’s quite at odds with the theory of evolution, which most Atheists want to accept. According to the theory of evolution, minds are the product of prior material processes. They’re later comers in the universe!
Here’s another tricky question for the Atheistic Idealist. Each of us has vivid and orderly experiences of a unified material world. If those experiences aren’t caused by real material objects, what are they caused by? Idealism says they ultimately must be caused by minds rather than material things. But which minds?
One possible answer is other human minds. But could all of your unique and complex experiences of the world really be caused by the minds of other human beings? That seems rather hard to swallow , not to mention quite disconcerting!
Another answer is your mind. It’s reasonable to think that some of your experiences and ideas are caused by your own mind (dreams, for example). Perhaps, then, all of your experiences and ideas are caused by your own mind. But if that’s the case, what need is there for any other mind to explain your experiences of the world? As more than a few philosophers of noted, Atheistic Idealism is in danger of sliding into solipsism, the view that your own mind is the only mind that really exists. But in that case, who really wrote this book?
One way out of this problem is to say that there is one absolute that causes every other mind to have orderly, coordinated experiences of a unified reality. But wouldn’t that be tantamount to admitting there is a God after all?”
(Anderson, What’s in a Worldview? 57-58)