Positivism and the Burden of Proof

When Alvin Plantinga was born in 1932, philosophy was in the grips of logical empir­icism. This doctrine, also known as logical positivism or simply positivism, held that all knowl­edge lies within the purview of science. One might think of positivists as having adopted an extreme form of John Locke’s under-laborer conception of the relationship between philos­ophy and science, on which “it is ambition enough [for a philosopher] to be employed as an under-laborer in clearing the ground a little, and removing some of the rubbish which lies in the way to knowledge” (Locke). To distinguish scientific from non-scientific questions, positivists used the verifiability principle, on which a question could be considered scientific if and only if it could be verified empirically. For the positivist, metaphysical questions such as, “Does God exist?” were simply meaningless.

This way of thinking has its roots in the Vienna Circle, a group of philosophers and scientists who met regularly at the University of Vienna and Café Central in Vienna, Austria, in the 1920s and 1930s. Three of the group’s most prominent members – Rudolf Carnap, Otto Neurath and Hans Hahn – published the unofficial manifesto of positivism in 1929, and in 1936 British philosopher A.J. Ayer, who was not officially a member of the group but was a public proponent of its ideas, brought positivism to the attention of the English-speaking world with his book Language, Truth, and Logic.

It is not difficult to imagine, then, that the presumption that pervaded academia at this time was that God did not exist. After all, anyone who argued that He did would necessarily be doing so on non-empirical – and therefore unverifiable – grounds. Indeed, most philosophers’ prior commit­ment to positivism had led them to rule out belief in God from the start, and the middle of the 20th century saw the percentage of theistic philosophers wane to near zero. This was not because theism is untenable, but rather because, within this ethos, the burden of proof necessarily fell on anyone whose ontology included that which could not be verified empirically. Science – defined as the method by which we conduct empirical investiga­tion – had come to be seen not as the primary source of knowl­edge, but as the only source of knowledge.

Positivism was not without its critics, however. Chief among these were Karl Popper (whom Neurath jokingly referred to as the “official opposition”) and W.V.O. Quine, an American philosopher whose 1953 book Two Dogmas of Empiricism is perhaps the seminal anti-positivist text. But philosophy advances notoriously slowly, and so the ideas in Two Dogmas had yet to take hold by the time Alvin Plantinga began work on his PhD in 1955. His first major book, God and Other Minds, took the world by storm in 1967. The book was at its core a rejection of positivism, which at this time was still the dominant worldview among philosophers.

God and Other Minds begins with a treatment of what Plantinga considers the best arguments for the existence of God – namely St. Anselm’s ontological argument, St. Thomas Aquinas’ cosmological argument, and the teleological argument – and concludes that none of them accomplish their intended goal.

But this does not matter: The proposition “God exists,” says Plantinga, is not one that can be shown to be true or false, at least not in the same way as a scientific claim such as, “The speed of light is 186,000 miles per second.” Instead, he believes the problem of God to be analogous to the problem of other minds, whose existence nearly everyone affirms (solipsists being the lone exception) despite a lack of empirical evidence.

This is the central thesis of the book. Plantinga argues that although one cannot prove empirically that other minds exist, it is still rational to believe in them, and that the same is true for the existence of God. It follows from this that there must be bases of knowledge outside empirical investigation. This conclusion was anathema to the positivist, whose entire epistemology revolved around a presumption of the omnipotence of empirical investigation.

But the question remains: Is this argument sound? For one, although Plantinga has revised some of the views he presents in the book (for example, he now advocates a modal version of the ontological argument), he still stands by the central thesis of the book. It was also well received by his fellow philosophers. Michael Slote, for example, in the January 1970 edition of The Journal of Philosophy called the book “one of the most important to have appeared in this century on the philosophy of religion” (Slote). What is more, the logic is elegantly simple: We believe (A) despite a lack of empirical evidence; it is rational to do so; therefore, it might also be rational to believe (B) despite a lack of empirical evidence. If one takes Plantinga’s goal to be restoring the viability of belief in God by dismantling the tyranny of the positivist regime, he certainly succeeded.

From within the positivistic framework of the day, however, the argument seemed analyt­ically false; that is, false by the meanings of the terms alone. After all, if science can explain everything there is to explain, there is necessarily nothing that science cannot explain. We now see that this logic is circular, but only because we have rejected positivism. If one of our most fundamental presuppositions about the world were that any talk of the metaphysical was a category error, this claim would seem self-evident.

It is tempting to look back on this period through a 21st-century lens and think of its adherents as somehow more unsophisticated than ourselves, but we must avoid this. Many of the past century’s greatest thinkers were positivists, at least for a time, for the simple reason that it is incredibly difficult to see outside the milieu in which one exists. But this is exactly what Quine and Plantinga did. And in my opinion, this makes their contribution to the field all the more impressive.

Possibly the most important upshot of God and Other Minds was a shifting of the burden of proof away from the theist. It was no longer incumbent upon the person arguing in favor of the possibility of the non-empirical to prove to their interlocutor that their entire worldview was based on an incomplete ontology. This meant that philosophers of religion were once again free to believe in the metaphysical, and therefore in God.

By the late 1970s, positivism was largely recognized to be an untenable position. Even A.J. Ayer, the aforementioned author of Language, Truth, and Logic and one of positivism’s most prominent advocates, said in an interview, “Well, I suppose the most important defect… was that nearly all of it was false.” We should be careful not to underestimate the role that Plantinga played in this change of heart.


Will Vickery is a senior philosophy and Spanish major at the University of Texas at Austin Liberal Arts Honors Program.

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