Scott Adams considers atheist irrationality from what I’d consider to be a rather quixotic entry point:
Allow me to summarize every discussion of atheism that has ever occurred on the Internet:
Atheist: “Religion is irrational.”
Believer: “Oh yeah? Atheism is a religion too, because it’s a cause that’s believed on faith! See Merriam-Webster’s 4th definition of religion.”
Atheist: “Atheism is religion the same way that NOT collecting stamps is a hobby.”
Believer: “You can’t prove the non-existence of God. And belief without proof is faith. Check Merriam-Webster’s second definition of faith. Therefore, atheists are irrational by definition.”
Atheist: “You can NEVER (or almost never) prove a negative. Besides, some things are so obvious that proof is unnecessary. Do you believe there’s a monster under your bed? You have no proof that it doesn’t exist. Therefore, by your reasoning, it’s only reasonable to believe there MIGHT be a monster under your bed.”
Believer: “Hey, you never know.”
To which I responded:
Given that the title of your post indicates that you may have encountered my column – soon to be a book – entitled “The Irrational Atheist” – please allow me to correct you here.
The irrationalism of atheism does not refer to its being a faith-based religion, although for many atheists this describes their adherence to sciencism rather nicely. Instead, it refers to the average atheist’s adherence to Christian morality, subtracting only some of the sexual aspects, despite having no rational basis for doing so.
(This is the point when most atheists will usually argue that one COULD construct a morality sans God, strangely, very few ever claim to have in fact successfully done so or can cite any successful constructions that aren’t a basic utilitarian pitfall. Nor do they explain the coincidental way in which their newly conceived morality so closely happens to resemble the wider morality in which they have been raised. As Joseph Heller wryly puts it, these “Scheisskopf” know exactly in which God they don’t believe.)
Atheists and agnostics who have actually thought the matter through, such as Voltaire, Sartre and Nietszche, have concluded that without a Divinely imposed morality, do what thou wilt shall indeed be the whole of the (moral) law. Voltaire, like Socrates, declares that this lack of belief should be limited to the elite, while Sartre dithers and Nietzsche rather more boldly embraces the logical conclusion. I daresay the German philosopher would conclude that the atheist who lives by Christian morality rather than the will to power is not only irrational, but a weak and cowardly fool at that.
Christian morality is not the Golden Rule. To love and obey God comes first and foremost, while “doing unto others” is merely a summary and a guide to behavior for those who know the least.
And though it is wildly offensive to those who think themselves the great servants of Reason, it is actually their irrationality in moral matters that speaks well of the basic character of most atheists. It is the rational atheists, those who put Nietzsche’s logic into practice, that the world does well to fear.
[It seems rational to do what feels good and has a good trade-off in risks and consequences regardless of how that feeling was germinated in you. So it seems rational to be a non-believer who prefers adhering to religious moral codes in the same way it’s rational to paint your house in your favorite color.
The problem here is that the moral behavior of the average atheist, as defined by the traditional Western morality, simply isn’t rational. There is no thought entering the process at all, it is merely unthinking adherence to the herd norms.
Unless you are a very unusual individual, you don’t refrain from engaging in an immoral action because you have rationally considered the morality of the matter, you refrain because a) you fear negative consequences, b) you have no interest in performing the action, or c) you are allowing the moral inertia of society to dictate your behavior.
What you describe as “seeming rational” to you is simple utilitarianism, which is a very poor substitute for God-based morality given the ease with which it can justify most actions that those subject to Western moral inertia would consider reprehensible.
For example, the Scott Adams who grew up in a society that practiced ritual child sacrifice would “rationally” engage in actions that the Scott Adams in this society would consider abominable. This is a great weakness of atheism as a philosophy and one of the reasons it is very unlikely to form the basis of a sustainable society, as it offers no fixed foundation for universal applicability.