Monday, 8 December 2014

Explain Hume’s idea of causation: if causation is just in the mind, why does it seem to function in the real world?

This paper deals with Hume’s idea of causation and its function in the real world.  Section I will give a brief summary of Hume’s idea of causation.  In section II, I will analyse how this concept of causation functions in the real world, real world meaning a world that exists independent of the mind.

I will argue that if we accept causation to be just in the mind, it functions somewhat dualistically; that is, causation can only seem to function with the aid of this world.  However because ‘seems to function’ does not certify that causation functions consistently, this paper will conclude that there is a semantic and perhaps epistemological problem with the word ‘seem’ and that faced with the initial question, causation ‘can’ only seem to function.

Hume’s idea of causation comes as an attack to the traditional metaphysician’s account that causation is necessarily connected.  Necessity implies a certain power behind causal events; that is to say should A cause B then there is a necessary connection between them.  But Hume is not happy with this idea.

For Hume, there are no a priori knowledge claims of causation; we simply cannot experience necessity within events.  Instead we can only base our claims on empirical knowledge; that is, experience of the world around us.  There is nothing in the world that we cannot imagine or experience without the aid of the external world, ‘ideas are images of our impressions’. (T 1.I.23).

Our ideas can only be derived from the world around us, and are copied into our minds.  For how can one know the taste of a pineapple without actually tasting one? (T 1.I 40) is a powerful argument by Hume – we simply cannot.

So, by rejecting this idea that power; that is necessary connection, exists behind the objects, all we experience are the objects unfolding before our senses in what seems to be in constant conjunction.  We observe the succession of objects, but we cannot observe its power or energy;  we simply cannot see fire ‘causing’ wood to charcoal; all we do see are two separate events, the fire followed by the wood appearance should they come into contact.  But this connection is not something we come to know with a single observation.  It is only on multiple observations of fire coming into contact with wood that we learn by ‘custom and habit’ (E 5) that there be a connection between them.  So every time we observe fire and wood, we make the connection that fire causes wood to burn.  The cause then is in the mind:

‘the idea of the one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other’(T 1.III.14)

It is through objects regularly displaying a pattern of events that trains us to, the more we are acquainted with these events, infer a connection between them, and hence a cause.  It is on past instances of observing patterns of causation that we presume there to be the same connection the next time we observe similar objects.  Hence, Hume defines cause as a form of regularity[1]:

‘an object, followed by another, and where all the objects similar to the first, are followed by objects similar to the second’. (E 9)


If causation resides in the mind, then why does it seem to function in the real world?  Hume’s definition of cause is twofold; firstly it implies the world functions in ways that appear to be regular; for example, the observation of a rapidly moving car hitting a person standing on the street will knock them down.  Secondly, our mind forms a connection between these two events taking place, because we assume in the future that all rapidly moving cars will knock people down.  Causation then functions somewhat dualistically; that is, we form a belief that A causes B by looking at the regularities around us.  In this sense, without the external world functioning the way it seems, we would not be able to apply a causal relationship.

 But Hume’s idea of causation is problematic for a number of reasons.  Firstly, it implies that events which appear itself regular are causally linked because ‘it determines the mind’ to form the idea that they are necessarily connected.  However, there are such cases where events appear to be regular but not causally linked at all.  Thomas Reid’s point that day follows night and night follows day is a classic example; they are both regular in conjunction of space and time – but neither day causes night or night day (Reid, 1788).  Therefore certain events in the world can mislead us into believing one to be the cause of the other; in this case, our idea of causation is dysfunctional when applied to the real world because they are not causally linked[2].  But Hume’s definition tells us that should we observe regularity in constant conjunction, then we should apply this missing connection as something causal.

Secondly, if we learn by ‘custom and habit’ that similar events in the past have produce similar effects, then we can only infer a certain probability that the same effect will occur in future instances.  Grey clouds in the past are associated with the fall of rain, but this is not to say that this will always happen every time we see a grey cloud.  Therefore should causation function in the real world, it does so due to our propensity to experience something as most likely to happen.  Therefore we can only assume to a degree that just because something has occurred in the past it will inevitably follow in the future.  But our minds are basic machines compared to nature as a whole, we only assume subconsciously that the chance in certain things occurring are probabilistic; we innocently take a leap of faith when we come to judge the real world, and in many everyday type cases we are correct in our inferences.  In a sense then, causation functions relatively blindly in the real world, for we can never actually prove with certainty that a similar cause will produce a similar effect; but paradoxically, it happens to functions with a good deal of accuracy.

On reflection of these points, causation seems to function in the real world as a form of scientific explanation.  Regularities that appear in the real world provide, to a certain extent at least, rules of nature which only the mind can conceive and interpret as laws.  These laws can then be formulated into equations of some kind in order to explain the cause of something.  For example, Newton’s second law of motion, F = ma, is a law that states that the force of an object in motion is equal to its mass multiplied by its acceleration[3].  The crux here is that force cannot be obtained without the initial observations of mass and acceleration in the first place.  Multiplying the mass of the object by its acceleration gives us the force for most, if not all, objects in motion.  But it is only the mind that provides an explanation of such a relationship between force and its constituent parts (mass and acceleration). 

It is in this sense then, should causation reside in the mind, it functions because it attempts to explain how nature operates; likewise, it frame’s laws that can back up our claims with evidence from the real world.

But the question is then, do we really invent these laws, or are we discovering them instead?  When we say we are discovering laws, what we are saying is that we are finding these laws ‘inside’ nature. The rules that describe events taking place are intrinsically embedded within her, waiting for our minds to come across them, to discover them.  However, should causation only dwell in the mind, its function must be to that of creating laws based on nature.  It is because only the mind can ‘glue’ events together to a certain degree of accuracy that justifies its function.  Causation then seems to work because we infer these physical laws which are initially interpreted from the phenomenon of nature that are more or less accurate in explaining why certain events happen.

A key problem impinging on this issue then is a semantic one: in the initial question what is meant exactly by the word “seem”? The word, in context of causation, means that causation seems to function in most cases, but there are times when it doesn’t; for example, Reid’s argument about the regularity of day and night.  Furthermore in regard to science and explanation, the laws we apply to nature only ‘seem’ to function in this point in time until they are refuted or improved upon.  In a sense then we are trapped inside a world of seeming.

In analysing this point it could be argued that the question: “if causation is just in the mind why does it seem to function in the real world” is a misguided or misplaced question since it is precisely because causation “seems” to function in the real world that Hume maintains it to be in the mind.


G, Strawson (1989), The Secret Connexion, Causation, Realism, and David Hume, Oxford: Clarendon Press

Hume, D., A Treatise of Human Nature, ed. D.F Norton and M.J Norton, 2007, New York: Oxford University Press Inc,

Hume, D., An Enquiry Concerning Human Understanding, ed. E. Steinberg (1977), 2nd Edition,  Canada: Hackett Publishing Company, inc.

Rosenberg, A (2005), Philosophy of Science a contemporary introduction, 2nd  Edition, London: Routledge.

Reid, T. Essays on the Active Powers of Man, in Beanblossom and Lehrer (1983), in M.J Loux (2006), Metaphysics a contemporary introduction, 3rd Edition, Oxon: Routle

[1] However, some philosophers disagree that Hume advocates a regularity theory such as G. Strawson (1989)
[2] It could be argued however that day and night are not entirely separate events; that is, the connection between them is due to the sun rise, which is only something we observe as ‘rising’.  The real “cause” is owed to the motion of the earth.  It could be interpreted that day is just the appearance of light given by the sun, and night is due to its absence – day and night are conditioned by the sun’s light.  Therefore day causing night is not entirely false as these are controlled by the earth’s rotation and the sun.
[3] A similar argument is provided  by A. Rosenberg, chapter 2 p.26.

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