David Hume’s Critique of Causality

David Hume

Philosophy in the modern era was made of rationalism and empiricism. Rationalist and empiricist disagreed in certain positions. One of these positions is the metaphysical concept of causality – that is, a thing (the cause) is the cause of the other (the effect), which implies a necessary connection between them which is one implying the other. This concept though was made popular in thee modern era, started by an ancient philosopher – Aristotle, whose writing was named metaphysics. On this note, David Hume, an empiricist and a Scottish philosopher argued against and re-posited. And it is upon this argument, that this work attempts an examination of Hume’s view.


Causality is the connection between two events or states such that one produces or brings about the other; where one is the cause and the other its effect. Also referred to as causation, it is the relation between an event (the cause) and a second event (the effect), where the second event is understood as a physical consequence of the first. This work, however, examines the background that led to Hume’s position on causality, a brief on David Hume and

DAVID HUME (1711-1776)

David Hume was born in Edinburgh in 1711. He is a Scottish philosopher. His philosophy was based on empiricist dictum that all ideas are copies of prior experience. As an empiricist, Hume had strong notion against causality and metaphysics as a whole. He is known for applying this standard rigorously to causation and necessity. Instead of taking the notion of causation for granted, Hume challenges us to consider what experience allows us to know about cause and effect.


Causality is a metaphysical concept in philosophy, and Hume, an empiricist does not believe in knowledge by reason – an instrument of metaphysics exercised upon what is referred to as causality – that is, a thing which produces the other. A distinction is often made between a cause that produces something new (e.g., a moth from a caterpillar) and one that produces a change in an existing substance (e.g., a statue from a piece of marble). Aristotle, whose writing was used to coin thee word metaphysics, distinguished four causes – efficient, final, material, and formal – that may be illustrated by the following example: a statue is created by a sculptor (the efficient) who makes changes in marble (the material) in order to have a beautiful object (the final) with the characteristics of a statue (the formal). Later philosophers developed other classifications of causes, often duplicative. The scientific conception that given circumstances under controlled conditions must inevitably produce standard results is generally accepted by philosophers. It is on this note that Hume argued, saying that in seeking to explain any object or event, we have evidence but no proof that its putative cause produced an effect on it.


His most important contributions to the philosophy of causation are found in “A Treatise of Human Nature”, and “An Enquiry concerning Human Understanding”, the latter generally viewed as a partial recasting of the former. Both works start with Hume’s central empirical axiom known as the Copy Principle. Loosely, it states that all constituents of our thoughts come from experience. Hume calls the contents of the mind perceptions, which he divides into impressions and ideas. Though Hume himself is not strict about maintaining a concise distinction between the two, we may think of impressions as having their genesis in the senses, whereas ideas are products of the intellect. Impressions, which are either of sensation or reflection (memory), are more vivid than ideas. Hume’s Copy Principle, therefore, states that all our ideas are products of impressions.

The Copy Principle only demands that, at the bottom, the simplest constituent ideas that we relate come from impressions. This means that any complex idea can eventually be traced back to Genesis constituent impressions. The Copy Principle only demands that, at the bottom, the simplest constituent ideas that we relate come from impressions. This means that any complex idea can eventually be traced back to Genesis constituent impressions.

In the Treatise, Hume identifies two ways that the mind associates ideas, via natural relations and via philosophical relations. Natural relations have a connecting principle such that the imagination naturally leads us from one idea to another. The three natural relations are a resemblance, contiguity, and cause and effect. Of these, Hume tells us that causation is the most prevalent. But cause and effect are also one of the philosophical relations, where the relata have no connecting principle, instead of being artificially juxtaposed by the mind. Of the philosophical relations, some, such as resemblance and contrariety, can give us certitude. Some cannot. Cause and effect are one of the three philosophical relations that afford us less than certain knowledge, the other two being identity and situation. But of these, causation is crucial. It alone allows us to go beyond what is immediately present to the senses and, along with perception and memory, is responsible for all our knowledge of the world. Hume, therefore, recognizes cause and effect as both a philosophical relation and a natural relation, at least in the Treatise, the only work where he draws this distinction.

The relation of cause and effect is pivotal in reasoning, which Hume defines as the discovery of relations between objects of comparison. But note that when Hume says “objects”, at least in the context of reasoning, he is referring to the objects of the mind, that is, ideas and impressions, since Hume adheres to the Early Modern “way of ideas”, the belief that a sensation is a mental event and therefore all objects of perception are mental. But causation itself must be a relation rather than a quality of an object, as there is no one property common to all causes or to all effects. By so placing causation within Hume’s system, we arrive at the first approximation of cause and effect. Causation is a relation between objects that we employ in our reasoning in order to yield less than demonstrative knowledge of the world beyond our immediate impressions. However, this is only the beginning of Hume’s insight.

In both the Treatise and the Enquiry, we find Hume’s Fork, his bifurcation of all possible objects of knowledge into relations of ideas and matters of fact. Hume gives several differentiae distinguishing the two, but the principal distinction is that the denial of a true relation of ideas implies a contradiction. Relations of ideas can also be known independently of experience. Matters of fact, however, can be denied coherently, and they cannot be known independently of experience.

A true statement must be one or the other, but not both since its negation must either imply a contradiction or not. There is no middle ground. Yet given these definitions, it seems clear that reasoning concerning causation always invokes matters of fact. For Hume, the denial of a statement whose truth condition is grounded in causality is not inconceivable (and hence, not impossible; Hume holds that conceivability implies possibility). For instance, a horror movie may show the conceivability of decapitation not causing the cessation of animation in a human body. But if the denial of a causal statement is still conceivable, then its truth must be a matter of fact, and must, therefore, be in some way dependent upon experience. Though for Hume, this is true by definition for all matters of fact, he also appeals to our own experience to convey the point. Hume challenges us to consider anyone event and meditate on it; for instance, a billiard ball striking another. He holds that no matter how clever we are, the only way we can infer if and how the second billiard ball will move is via past experience. There is nothing in the cause that will ever imply the effect in an experiential vacuum. And here it is important to remember that, in addition to cause and effect, the mind naturally associates ideas via resemblance and contiguity. Hume does not hold that, having never seen a game of billiards before, we cannot know what the effect of the collision will be. Rather, we can use resemblance, for instance, to infer an analogous case from our past experiences of transferred momentum, deflection, and so forth. We are still relying on previous impressions to predict the effect and therefore do not violate the Copy Principle. We simply use resemblance to form an analogous prediction. And we can charitably make such resemblances as broad as we want. Thus, objections like: Under a Humean account, the toddler who burned his hand would not fear the flame after only one such occurrence because he has not experienced a constant conjunction, are unfair to Hume, as the toddler would have had thousands of experiences of the principle that like causes like, and could thus employ resemblance to reach the conclusion to fear the flame.

If Hume is right that our awareness of causation (or power, force, efficacy, necessity, and so forth – he holds all such terms to be equivalent) is a product of experience, we must ask what this awareness consists in. What is meant when some event is judged as cause and effect?  Strictly speaking, for Hume, our only external impression of causation is a mere constant conjunction of phenomena, that B always follows A, and Hume sometimes seems to imply that this is all that causation amounts to. Nevertheless, ‘causation’ carries a stronger connotation than this, for constant conjunction can be accidental and therefore doesn’t get us the necessary connection that gives the relation of cause and effect its predictive ability. We may therefore now say that, on Hume’s account, to invoke causality is to invoke a constant conjunction of relata whose conjunction carries with it a necessary connection.


Hume posits that the necessary connection invoked by causation is nothing more than this certainty. Therefore, his Copy Principle demands that an idea must have come from an impression, but we have no impression of efficacy in the event itself. Instead, the impression of efficacy is one produced in the mind. As we experience enough cases of a particular constant conjunction, our minds begin to pass a natural determination from cause to effect, adding a little more “oomph” to the prediction of the effect every time, a growing certitude that the effect will follow again. It is the internal impression of this “oomph” that gives rise to our idea of necessity, the mere feeling of certainty that the conjunction will stay constant. Ergo, the idea of necessity that supplements constant conjunction is a psychological projection. We cannot help but think that the event will unfurl in this way.


  1. Ayers, M. (1996). “Natures and Laws from Descartes to Hume”, in The Philosophical Canon in the Seventeenth and Eighteenth Centuries: Essays in Honour of John W. Yolton, edited by G.A.J. Rogers and S. Tomaselli, New York: University of Rochester Press.

  2. Mackie, J. L. The Cement of the Universe- A Study of Causation. Oxford University Press Clarendon, New York, New York, 1980

  3. Psillos, S. (2002). Causation and Explanation. Montreal: McGill-Queen’s University Press.

  4. Paul, E. & Pap, A. (eds) (1975). A Modern Introduction to Philosophy: New York, The Free Press.

  5. Windt, P.Y. (1982). An Introduction to Philosophy: Ideas in Conflict; New York, West Publishing Company.

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