Sigmund Freud (b.1856 – d.1939) is well-known as the father of Psychoanalysis and a key intellectual figure in the secularization of Western culture. His reputation as an atheist and outspoken critic of religion is among the ranks of Friedrich Nietzsche and Karl Marx, both of whom viewed belief in God as a crutch for weak-minded people.
Some modern day psychiatrists speculate that Freud’s early childhood experiences predisposed him to reject his Jewish heritage and adopt an atheistic philosophy of life. For example, Armand M. Nicholi – Associate Clinical Professor of Psychiatry at Harvard Medical School – argues that Freud’s atheism was shaped by social factors such as early childhood poverty and anti-Semitisim, as well as by psychological factors issuing from abandonment by his nanny and hostility toward his father.
But perhaps the most important factor in the development of Freud’s atheism was his understanding of science. In his New Introductory Lectures on Psychoanalysis (1933), Freud argued that the scientific method was the only way we could truly come to know things. In an oft quoted passage, he writes that “there are no sources of knowledge of the universe than the intellectual working over of carefully scrutinized observations, what we call research…” (p.159). Elsewhere, in The Future of An Illusion (1927) he states, “Our science is not illusion, but an illusion it would be to suppose that what science cannot give us we can get elsewhere.”
Freud thought that belief in God was problematic if human knowledge was restricted to the methods of science. Why? Because God is (by definition) a non-empirical entity, unable to be measured through observation and experimentation. And if so, then God’s existence cannot be proved or disproved by science. Ironically, Freud failed to recognize that this conclusion only warranted agnosticism about God, not atheism. Be that as it may, his understanding of science (which I call “scientism”) faces five serious objections:
1. Scientism is self-refuting
As Keith Ward points out in his book Pascal’s Fire (2006), “The belief that you should only believe things on the basis of observation and experiment is not itself based on observation and experiment, and therefore it is stating that it should not itself be believed” (p.118).
2. Science presupposes the five senses as its starting point
Science can’t even begin unless the faculties of sight, hearing, touch, smell, and taste are taken as a given. Yes, each of the senses can be questioned, corrected and augmented by new discoveries, but these discoveries would be inaccessible without relying on our senses at some point. For example, when a stick appears bent in water, we can touch the stick to confirm that it is straight, despite what our eyes tell us. But we can’t question all of our senses at once, since if we did, we’d have no further empirical basis on which to question them! So the idea that our sense experience is a starting point for science is a true idea, just not a scientifically verifiable one. It’s a philosophical idea.
3. Science can’t ground its logic of explanation
Scientific theories rely on the logical principles of deduction, induction, and abduction to explain the observable data. But the theories themselves can’t explain the principles of explanation they depend on – that would be circular reasoning! The basis for these principles is the purview of philosophy, not science.
4. The concept of “observability” is slippery
At various points in human history, phenomena which were unobservable are now considered to be objects of scientific inquiry. Distant galaxies, cells, genes, and atoms were once unobservable, but advances in the technology of telescopes and microscopes have now solved that problem. Moreover, theoretical entities (e.g. baryon particles) have played an important role in the success of scientific knowledge over the past two hundred years, but their existence is inferred by observing their effects, not by direct measurement. They are posited by scientists abductively, by means of inferences to the best explanation. But if it is legitimate to explain observed phenomena as the effects of unobservable entities, then why is it illegitimate to posit the existence of God as an unobservable entity whose existence is said to produce observable effects in the natural world? Within the context of abductive reasoning, then, the fact that God is a non-empirical entity in no way rules God out as an explanation.
5. Scientism undermines moral knowledge
Science can explain why a physical event occurs or obtains. But is cannot tell us whether it ought to happen or whether something is morally good or bad. It can describe the most efficient way to kill a human being with a scalpel, but it can’t tell you whether you should or shouldn’t kill that person. Thus, if there are moral truths at all, we can’t know them because they can’t be discerned through scientific means. [Note: perhaps knowledge of beauty, aesthetics, and purpose would be similarly undermined by Freud’s constraints]
For these five reasons, Freud’s scientism is untenable. It restricts the scope of human knowledge to scientific knowledge – but we have good reasons to reject that restriction.
 Nicholi, Armand. The Question of God: C.S. Lewis and Sigmund Freud Debate God, Love, Sex, and the Meaning of Life. Free Press: 2003
 Freud, S. (1933). New Introductory Lectures on Psychoanalysis (W.J.H. Sprott, Trans). New York: Norton.