David Hume
David Hume

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4.3 Physical grounds for thinking we are immortal

In section III Hume discusses what he calls physical reasons for thinking there is an afterlife. A sensible guess as to what he means by a physical reason is that it is one based on observation and experience of the physical world. He begins by asserting that physical reasons are the ones he has most respect for. (This assertion is unsurprising: his objections to moral reasons, and the metaphysical reasons we skipped, turn on the allegation that they depend on claims that go beyond what is observable.) He goes on to claim, further, that all evidence that is based on observation – all ‘physical’ evidence – points not towards there being an afterlife, but rather towards our being fully mortal.

Before looking at how Hume seeks to vindicate this further claim, it will help to have a better appreciation of how he thinks we reason from experience. For although I have stressed the importance to Hume and his contemporaries of treating experience as the sole source of evidence, I have not said much about how reasoning from observation is supposed to work.

Consider how, whenever we have touched snow in the past, we have felt coldness. These past experiences tell us that the next time we touch snow, it will once again feel cold. Or at least that is what we think they tell us. That is because we are tacitly using what Hume calls the rule of analogy. (It later came to be called a principle of induction, but I will keep to Hume's terminology.) The rule of analogy is named but not explicitly stated by Hume in this essay. According to it:

If all experiences of one type (e.g. seeing snow) have been followed by an experience of another type (e.g. feeling it to be cold) in the past, then experiences of the first type will be followed by experiences of the second type in the future.

It is thus a rule of reasoning that allows us to infer from what we observed already to what we have not yet observed.

It is no exaggeration to say that early empiricists held this rule of analogy, or some variant of it, to be the golden gateway to all genuine knowledge. The legitimacy of analogical reasoning is what, according to many, lay at the heart of the success of the scientific method. By conducting experiments and observing the results, scientists were able to make accurate predictions about the future, building theories on that basis. Hume too takes this rule of reasoning to be central to scientific advancement. He doesn't think rules of reasoning can get any more basic than this one. What we must now turn to is Hume's application of the rule to the question of our immortality.

In paragraphs 18–19, Hume makes his first application of the rule to the question of our mortality. It is also the most complex; be prepared to skip to the second application rather than become bogged down in this first application. The key passage is:

Where any two objects are so closely connected that all alterations which we have ever seen in the one, are attended with proportionable [i.e. proportional] alterations in the other, we ought to conclude by all rules of analogy, that, when there are still greater alterations produced in the former, and it is totally dissolved, there follows a total dissolution of the latter.

The relevant ‘two objects’ are the mind and the body. Hume's basic idea is this. The mind and the body show ‘proportionable’ alterations: as the body grows feeble so does the mind (or soul), and so they can also be assumed to ‘dissolve’ (by which Hume appears to mean ‘to cease to exist’) together. From this he concludes that when the body ceases to function entirely, or ‘dissolves’, so does the mind. The complexity comes with trying to see how this is an application of the rule of analogy as I have stated it above.

To see that it is, consider what the relevant previous experiences are. Hume does not bother to say what he has in mind, but we can help him out here:

The forward acceleration of a bicycle is proportional to the force applied to its pedals; elimination of this force leads to elimination of acceleration.

The population size of the fish in a pond varies in proportion to the quantity of water; elimination of water leads to elimination of fish.

In all our previous experience, Hume is claiming, whenever alterations between two objects are ‘proportionable’, it is also the case that total dissolution of the one object is accompanied by total dissolution of the other. And now the rule of analogy tells us to infer that this will be the case in the future too. Thus, if all experiences of one type (e.g. alterations between two objects being proportional) have been followed by an experience of a second type (e.g. total dissolution of the one object being accompanied by total dissolution of the other) in the past, then experiences of the first type will be followed by experiences of the second type in the future.

The future case he has in mind is that of the soul when the body ‘dissolves’. The proportionality or close interconnection observable between soul and body must mean that the dissolution of the body will be accompanied by the dissolution of the soul.

Exercise 8

Read to the end of paragraph 19. (The next question is optional; you may prefer instead to jump straight to Hume's second application of the rule of analogy in paragraph 20, which I examine below.) Why in paragraph 19 does Hume list some ways in which deterioration in the functioning of the body is often accompanied by deterioration in the functioning of the soul (or mind): in sleep, in infancy, in sickness and in ageing?


The sharpness of the human mind is observed always to match or be proportional to the robustness of the human body, he claims. By the rule of analogy, based on other examples that he doesn't make explicit (such as the bicycle or fish examples above), he thinks it reasonable to conclude that when the body declines completely, the mind (or soul) ceases to exist as well.

A second and more straightforward application of the rule of analogy can be found in paragraph 20. There are many observable situations in which transplanting something into a new and alien environment tends to kill it. We don't see fishes surviving away from water or trees thriving beneath water. In other words, a change to an organism's environment is always associated with a change in its capacity to thrive. The bigger the change in the environment, the more likely it is that the organism will cease to exist. Given this, says Hume, why should we expect the soul to be able to survive without its body? Loss of our bodies is the biggest change we could possibly undergo, making it more likely that we simply cease to exist entirely.

Exercise 9

Read up to the end of paragraph 20. (The following question is optional unless you skipped the optional question in the previous exercise.) Hume suggests in paragraph 20 that a purely spiritual, bodiless afterlife is even less plausible than metempsychosis, the transmigration of the soul from one body to another, perhaps across species boundaries. What are his grounds for this claim?


A change of environment is always detrimental to the thing moved. Moving to a new body is less of a change than ceasing to have any body at all. So it is more plausible that we could survive migration to another body than that we cease to be embodied at all. This is true even if the new body is an animal's, since animals’ bodies bear many similarities to our own.

Figure 5
Figure 5 Jean-Baptiste Greuze, The Paralytic, 1763, oil on canvas, 115.5 x 146 cm, The State Hermitage Museum, St Petersburg. Photo: Scala

Metempsychosis (mentioned jestingly by Hume), in which souls migrate from body to body across species boundaries after each successive death, was one of several popular secular alternatives to Christian conceptions of the afterlife. Another is expressed in this painting: that we can live on in our children. The presence of the Bible on the left of the painting is swamped by the presence of the children. This doctrine of filial piety was even associated with a moral injunction: if you are good in this life (i.e. raise your children well), your survival into posterity will be all the more assured. This is explicit in the title Greuze gave to a preparatory study for the painting, ‘The fruits of a good education’.

The remainder of section III contains three diverse objections to the theory that we survive beyond our death. The relation of these to the rest of the essay is slim, and Hume is occasionally only half-serious when he presents them. We can proceed through them quite quickly.

In paragraph 21 Hume asserts that supporters of the thesis that we have an afterlife have an accommodation crisis: the place where souls go will be populated by an ever-growing number of individuals. Ready replies to this thought were available at the time. Since souls are supposedly immaterial, by definition this means they do not occupy space so there would be no danger of overcrowding. Moreover, what justification had Hume for supposing that heaven or hell had a limited size?

In a different objection (paragraph 22), he suggests that our soul's non-existence prior to birth increases the probability of its non-existence after death. This is the opinion attributed to him by Boswell, as quoted above (‘David Hume said to me he was no more uneasy to think he should not be after this life, than that he had not been before he began to exist.’). Hume offers some discussion of this in section I of his essay (paragraph 5), which we are not focusing on. No further support is provided in the present paragraph, just a quotation from a classical source.

In paragraph 23 Hume is implicitly responding to an attitude that would have been common. Fear of death in a person was assumed to be evidence in favour of their belief in an afterlife in which non-believers are damned. Fear of death could therefore reveal a profession of agnosticism to be disingenuous. This, in part, is why people were so curious about whether Hume would recant his views on his deathbed.

Hume makes the point that belief in an afterlife is not the only available explanation of fear of death. This fear could be accounted for easily enough as attachment to happiness in this, the only, life. (In fact, he says, many of those who do believe in an afterlife should be placid, since for them our mortal death is not really the end of our existence.) In view of this claim, Hume went beyond the call of duty in dying with:

great cheerfulness and good humour and with more real resignation to the necessary course of things than any whining Christian ever died with pretended resignation to the will of God.

(Adam Smith, letter to Alexander Wedderburn, 14 August 1776, quoted in Mossner and Ross, 1987, p. 203)

Paragraph 23 ends with a speculation: it is a passionate hope to live on that irrationally gives rise in us to a belief that we do live on. Paragraph 24 merely repeats earlier material, and the ironic final paragraph has been discussed already.

Exercise 10

Finish reading to the end of the essay. How persuaded are you by his discussion of fear of death in paragraph 23?


You will almost certainly have come up with your own conclusion, but here is mine: Hume is unfair in suggesting that fear of death is incompatible with belief in an afterlife. Fear of death could easily be explained as fear of the possibility of an eternity of pain. It needn't be put down to an irrational attempt to match false hopes with false beliefs.

You should by now appreciate just how careful a writer Hume was. Aside from one or two light-hearted paragraphs near the end, not a single sentence is included that doesn't have an important purpose. Every paragraph develops his case in some unpredictable but thoughtful way. Repetition is minimal. That is why we have gone through the essay in such a painstaking way, paragraph by paragraph. All the same, it helps to step back and gain an appreciation of the whole essay, and in the next exercise you are asked to read it through in a single sitting.

Exercise 11

Reread ‘Of the Immortality of the Soul [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ’ from beginning to end (omitting section I). Look out for the three objections to the moral reasoning in section II, and the role of Hume's appeals to experience as the final arbiter throughout the essay.


It is unlikely you will understand the point Hume is trying to make in every paragraph. But do make a mental note of how much of the essay you now more or less understand. When you have finished, recall your reaction to the exercise on p. 179. I hope this will reveal the extent to which an apparently obscure piece of writing may in fact contain a carefully constructed discussion, which careful study can render accessible.

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