Truth

Modern, post-modern, post-truth: that’s sometimes said to be the era we’re now living in. Our disagreements don’t stop at our ideals, but extend to basic facts about our situations. Unable to persuade each other of those facts, we resort to frustratedly expressing that the facts are facts. Not believing them doesn’t change them. There is only one absolute truth.

What is this ‘absolute truth’ and should we really care about it? In the philosophy of early modern Europe, the first of those questions had a natural answer. ‘Absolute truth’ meant what God believed, or what was true from a God’s-eye perspective. The secular descendent of this idea is that absolute truth is what we would believe if we were not limited in the ways that human beings are. Some early moderns did think that God’s perspective was the one we should aspire to. We might include in that category the likes of John Locke (1632–1704), Baruch Spinoza (1632–1677), and Gottfried Leibniz (1646–1716). In the space I have, however, I want to focus on three philosophers of the period who, in somewhat different ways, denied that absolute truth was really something we should care about.

René Descartes (1596–1650) was born in France, worked in the Dutch Republic, and died in Sweden. His most celebrated work is the Meditations, which aims to find a secure footing for human knowledge. Descartes begins by trying to show which of our beliefs are not secure. This is where the famous evil demon comes in: an imagined malign power which could convince us of anything. It might not just deceive our senses, but make us think that we’re reasoning logically when instead we’re wading in nonsense. Descartes thinks that such a demon is conceivable, and since it would be able to convince us of anything, it might seem to follow that we have no secure beliefs. Not so, says Descartes: there are claims which I cannot doubt, such as that I think. What Descartes means by this is that there are some doubts we just aren’t wired to take seriously. He still gives arguments of sorts against taking those doubts seriously, but our faith in those arguments still, in the end, comes down to our psychology.

Jacques Lubin, after Frans Hals. René Descartes. 1649. Line Engraving. National Portrait Gallery, London D28637.

It might seem like Descartes is missing the point or being overly pedantic here. Whilst there is a sense in which those beliefs we’re not capable of seriously doubting are ‘secure’, the kind of security we are after in our knowledge might, perhaps, be more like that of knowing that it’s absolutely true. Marin Mersenne (1588–1648), a friend of Descartes now best known as a mathematician, pressed this point to him. Descartes’ response, in the second set of replies he published with the Meditations, was straightforward and sensible. If we have beliefs we cannot doubt, then there’s simply no point in asking whether we ought to doubt them. If they clash with absolute truth, then so much the worse for absolute truth. All that would show is that absolute truth is not a standard we can hold ourselves to. A common thought, then and now, about standards we can’t hold ourselves to is that they can’t be ones we ought to try to hold ourselves to, either. That thought seems clearly at work in Descartes’ reply here to Mersenne.

It also seems to be at work in the thought of David Hume (1711–1776), writing in Scotland a century later. Hume was an empiricist: a sceptic about reason as an ultimate source of concepts and knowledge. Hume thought that there was no rational reason for us to believe that the Sun will rise tomorrow. To have a rational reason to believe that, the process of inductive inference would need to be rational. Inductive inference means concluding that there is some rule on the basis of past cases which fit it. For example, the Sun has always risen in the past: we might infer that it always will. The challenge with these kinds of inferences, says Hume, is they depend on an assumption which we don’t know is true. That assumption is that the future will resemble the past, at least in relevant ways.

David Martin, after Allan Ramsay. David Hume. 1767 (1766). Mezzotint. National Portrait Gallery, London D32392.

Hume concludes that we make this assumption as a matter of ‘custom’ or human nature. Hume doesn’t take that conclusion, though, to undermine inductive inference as a method. Rather, he thinks that we have no way of knowing if the assumption is true or false; it isn’t grounded in reason, but we also can’t know it from experience: we’d need experience of the future. In other words, Hume takes the absolute truth of the validity of induction to be out of reach for us. Because it’s out of reach, there’s no point in asking whether we ought to reason using induction. On this and other questions, Hume thinks absolute truth isn’t something we should care about.

The end of the early modern era in European philosophy is often marked by Immanuel Kant (1724–1804). Kant wrote in German in what was then Prussia but is now the Russian exclave of Kaliningrad. Part of the difficult argument of Kant’s Critique of Pure Reason is that the way the world is from our human perspective simply cannot be an approximation of a God’s-eye, absolutely true view of it. If we idealise our own perspective, we run into contradictions or ‘antinomies’. Think of how arguments for a first cause contradict themselves in supposing both that all things have a cause and one thing doesn’t. Kant thinks his antinomies show a God’s-eye perspective must be different fundamentally to our own. We can’t try to bring our own view in line with God’s: those views must be radically, structurally different. Instead of holding up God-like absolute truth as a standard for our beliefs or knowledge, we need to find alternative standards to set for our distinctly human knowledge.

Descartes, Hume, and Kant don’t agree on what those standards for our knowledge or beliefs should be. Descartes thinks that what we should believe is what we clearly and distinctly perceive. Hume thinks we can have our natural views and just remove from them confusions of reason. Kant thinks we should have two ways of seeing the world, one in which we’re passive and one in which we’re agents. Perhaps the lesson of these early moderns, then, is that the messiness of truth isn’t just on the surface. It’s not just messy sometimes what the facts are or what are the appropriate standards of evidence. It’s messy what truth itself is, taking truth to still be what we would ideally believe. When the early moderns turned away from God, in that way, they made the messiness of truth complete.

Adam J Roberts is a PhD Candidate in the Department of Philosophy at King’s College London.

5 March 2021.