There seems to be a widespread assumption throughout much of the Western intellectual community that belief in God is based on all kinds of irrational immature needs and wishes, but atheism or skepticism is derived from a rational, no-nonsense appraisal of the way things really are.
    -Professor Paul C. Vitz, The Psychology of Atheism

It seems to me, that the only objects of the abstract science or of demonstration are quantity and number, and that all attempts to extend this more perfect species of knowledge beyond these bounds are mere sophistry and illusion. As the component parts of quantity and number are entirely similar, their relations become intricate and involved; and nothing can be more curious, as well as useful, than to trace, by a variety of mediums, their equality or inequality, through their different appearances. But as all other ideas are clearly distinct and different from each other, we can never advance farther, by our utmost scrutiny, than to observe this diversity, and, by an obvious reflection, pronounce one thing not to be another. Or if there be any difficulty in these decisions, it proceeds entirely from the undeterminate meaning of words, which is corrected by juster definitions. That the square of the hypothenuse is equal to the squares of the other two sides, cannot be known, let the terms be ever so exactly defined, without a train of reasoning and enquiry. But to convince us of this proposition, that where there is no property, there can be no injustice, it is only necessary to define the terms, and explain injustice to be a violation of property. This proposition is, indeed, nothing but a more imperfect definition. It is the same case with all those pretended syllogistical reasonings, which may be found in every other branch of learning, except the sciences of quantity and number; and these may safely, I think, be pronounced the only proper objects of knowledge and demonstration.

All other enquiries of men regard only matter of fact and existence; and these are evidently incapable of demonstration. Whatever is may not be. No negation of a fact can involve a contradiction. The non-existence of any being, without exception, is as clear and distinct an idea as its existence. The proposition, which affirms it not to be, however false, is no less conceivable and intelligible, than that which affirms it to be. The case is different with the sciences, properly so called. Every proposition, which is not true, is there confused and unintelligible. That the cube root of 64 is equal to the half of 10, is a false proposition, and can never be distinctly conceived. But that C¾sar, or the angel Gabriel, or any being never existed, may be a false proposition, but still is perfectly conceivable, and implies no contradiction.

The existence, therefore, of any being can only be proved by arguments from its cause or its effect; and these arguments are founded entirely on experience. If we reason a priori, anything may appear able to produce anything. The falling of a pebble may, for aught we know, extinguish the sun; or the wish of a man control the planets in their orbits. It is only experience, which teaches us the nature and bounds of cause and effect, and enables us to infer the existence of one object from that of another. Such is the foundation of moral reasoning, which forms the greater part of human knowledge, and is the source of all human action and behaviour.

The central concept in Freud's work, aside from the unconscious, is the now well-known Oedipus Complex. In the case of male personality development, the essential features of this complex are the following: Roughly in the age period of three to six the boy develops a strong sexual desire for the mother. At the same time the boy develops an intense hatred and fear of the father, and a desire to supplant him, a "craving for power." This hatred is based on the boy's knowledge that the father, with his greater size and strength, stands in the way of his desire. The child's fear of the father may explicitly be a fear of castration by the father, but more typically, it has a less specific character. The son does not really kill the father, of course, but patricide is assumed to be a common preoccupation of his fantasies and dreams. The "resolution" of the complex is supposed to occur through the boy's recognition that he cannot replace the father, and through fear of castration, which eventually leads the boy to identify with the father, to identify with the aggressor, and to repress the original frightening components of the complex.

It is important to keep in mind that, according to Freud, the Oedipus complex is never truly resolved, and is capable of activation at later periods-almost always, for example, at puberty. Thus the powerful ingredients of murderous hate and of incestuous sexual desire within a family context are never in fact removed. Instead, they are covered over and repressed. Freud expresses the neurotic potential of this situation:

The Oedipus-complex is the actual nucleus of neuroses . . . What remains of the complex in the unconscious represents the disposition to the later development of neuroses in the adult.

In short, all human neuroses derive from this complex. Obviously, in most cases, this potential is not expressed in any seriously neurotic manner. Instead it shows up in attitudes toward authority, in dreams, slips of the tongue, transient irrationalities, etc.

Now, in postulating a universal Oedipus complex as the origin of all our neuroses, Freud inadvertently developed a straightforward rationale for understanding the wish-fulfilling origin of rejecting God. After all, the Oedipus complex is unconscious, it is established in childhood and, above all, its dominant motive is hatred of the father and the desire for him not to exist, especially as represented by the desire to overthrow or kill the father. Freud regularly described God as a psychological equivalent to the father, and so a natural expression of Oedipal motivation would be powerful, unconscious desires for the nonexistence of God. Therefore, in the Freudian framework, atheism is an illusion caused by the Oedipal desire to kill the father and replace him with oneself. To act as if God does not exist is an obvious, not so subtle disguise for a wish to kill Him, much the same way as in a dream, the image of a parent going away or disappearing can represent such a wish: "God is dead" is simply an undisguised Oedipal wish-fulfillment.

Since both believers and nonbelievers in God have psychological reasons for their positions, one important conclusion is that in any debate as to the truth of the existence of God, psychology should be irrelevant

For men, God seems to function primarily as a principle of justice and order in the world--and only secondarily as a person with whom one has a relationship. In other words, God's law and providential control seem to be the central aspects of belief for men. [...]

We would expect, therefore, that men who become atheists will find a new absolute principle with which to order the world. Thus, we expect male atheists to be quite explicitly atheistic and to have a new "divinity" that takes the intellectual place of God. As a consequence, atheistic men should be intense believers in such alternative principles as reason, science, progress, humanism, socialism, communism, or existentialism. And this is what we see in the lives of the atheists.