Quarantining Scepticism

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   We are looking for people who are aware of the power of sceptical doubts, have not tried to dispel them (for example by inventing principles like the uniformity of nature, theories of inductive support or probability) have not become sceptics, but have merely isolated scepticism - perhaps then proposing unsupported presuppositions like Tp.

   Locke was well aware of the sceptical doubts of which Hume was later to make so much. He wrote (pp.392-3) (by 'demonstration' we take him to mean logical proof): "Folly to expect Demonstration in everything . Whereby yet we may observe how foolish and vain a thing it is for a man of a narrow knowledge, who having reason given him to judge of the different evidence and probability of things, and to be swayed accordingly, to expect demonstration and certainty in things not capable of it; and refuse assent to very rational propositions, and act contrary to very plain and clear truths, because they cannot be made out so evident, as to surmount every the least (I will not say reason) pretence of doubting. He that, in the ordinary affairs of life, would admit of nothing but direct plain demonstration, would be sure of nothing in this world, but of perishing quickly. The wholesomeness of his meat or drink would not give him reason to venture on it; and I would fain know what it is he could do upon such grounds are capable of no doubts, no objection".
   Newton (quoted in Blake, Ducasse, and Madden p.142) wrote in 'Principia ', as his Third Rule of Philosophising: "For since the qualities of bodies are only known to us by experiments, we are to hold for universal all such as universally agree with experiments; and such as are not liable to diminution can never be quite taken away. We are certainly not to relinquish the evidence of experiments for the sake of dreams and fictions of our own devising; nor are we to recede from the analogy of Nature, which uses to be simple, and always consonant with itself". There is a reference here to the uniformity of nature, but Newton seems to me to be unconvinced that this provides any kind of justification. Consider his Fourth Rule (p.123): "In experimental philosophy we are to look upon propositions collected by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions. This rule we must follow, that the argument of induction may not be evaded by hypotheses".  Though, once again, an alternative plausible interpretation of this passage is that Newton is referring to alternative conventional theories, rather than the bizarre alternatives sanctioned if inductive presuppositions are denied.

   Or, most strikingly, in the Opticks , (p.123): "...drawing general conclusions from them by induction, and admitting of no objections against the conclusions, but such as are taken from experiments, or other certain truths ..... And although the arguing from experiments and observations by induction be no demonstration of general conclusions; yet it is the best way of arguing which the nature of things admits of, and may be looked upon as so much the stronger, by how much the induction is more general". In other words, once evidence has supported our generalisation, we should accept it, pro tem , despite knowing that 'hypotheses', such as those raised by sceptics, can always be invented which we cannot demonstrate to be false, and which will cast doubt on the truth of our generalisation. He is objecting to "What if...?" criticisms, unsupported by evidence. But his justification for this objection is so scanty, that we feel he is virtually saying that such 'hypotheses' should be quarantined by fiat. A hint of impatience with speculators, expressed by a practical investigator, is characteristic of this attitude.

   Whewell (1968) wrote (p.152) "Men cannot help believing that the laws laid down by discoverers must be in great measure identical with the real laws of nature, when the discoverers thus determine effects beforehand in the same manner in which nature herself determines them when the occasion occurs .... Such a coincidence of untried facts with speculative assertions cannot be the work of chance, but implies some large portion of truth in the principles on which the reasoning is founded".
   Whewell is aware of the need for Tp. He is also implicitly aware that it lacks justification, because he is reduced to (a) referring to what people "cannot help believing" (b) waving the word 'cannot' hopefully at us.
   The reference to "coincidence" shows his appreciation of the role of a probability judgement - of Tp.

   Duhem, writing of the universal human feeling that a true natural classification possess some order or unity, said (p.104 (1974): "whoever would see in this nothing more than a snare or a delusion ... would be excommunicated by common sense. In this situation, as in all others, science would be impotent to establish the legitimacy of the principles themselves which outline its methods ... were it not to go back to common sense". He suggests that this common sense cannot actually be logically justified, but that if physicists thought that all they could do was to devise pragmatic hierarchies, convenient for summarising observations but not true, they would hardly bother, they (p.334): "would stop devoting (their) time and efforts to a work of such meagre importance ... The merely logical dissection of theory cannot discover the fissure through which this knowledge ... is introduced into the structure of physics".

   Poincaré (1905) writes (p.412) "When we wish to check a hypothesis, what do we do? We can not verify all its consequences, since they would be infinite in number; we content ourselves with verifying certain ones and if we succeed we declare the hypothesis confirmed, because so much success could not be due to chance ... Is this a simple illusion of ours, or are there cases where this way of thinking is legitimate? We must hope so, else were all science impossible." (p.96) We do not believe that simplicity has appeared in phenomena by chance; "we should not believe that nature had acted expressly to deceive us". (p.133) "We have verified a simple law in a good many particular cases; we refuse to admit that this agreement, so often repeated, is simply the result of chance ... Kepler noticed that a planet's positions, as observed by Tycho, all lay on one ellipse. Never for a moment does he have the thought that by a strange play of chance Tycho never observed the heavens except at the moment when the real orbit of the planet happened to cut this ellipse ... To refuse to do this would be to attribute to chance an inadmissible role". (p.157) "All the sciences (are) only unconscious applications of the calculus of probabilities. To condemn this calculus would be to condemn the whole of science* ... (this calculus is the expression of an "obscure instinct which we may call 'good sense'." "We cannot do without this obscure instinct". p.154 "In a multitude of circumstances the physicist is in the same position as the gambler who reckons up his chances".  (*Howson and Urbach use this as the opening quotation in their Scientific Reasoning. The choice is apposite in terms of the calculus, but less so in terms of the Tp, which they try (unsuccessfully) to justify)
   This is precisely the view of the rôle of, the lack of justification of, and the need to quarantine, Tp that we are supporting.

   Russell (1931) wrote (p.78): " Induction remains an unsolved problem of logic. As this doubt, however, affects practically the whole of our knowledge, we may pass it by ..."

   Popper wrote, in his 1972 (p. 29)"...what has to be given up is the quest for justification , in the sense of the justification of the claim that a theory is true" (italics in original); p 75 "There simply are no sufficient reasons for holding these hypotheses {the natural sciences, such as physics} to be true, let alone certainly true"; p.77 "Thus there is nothing like absolute certainty in the whole field of our knowledge". He thus takes the view that sceptical doubts cannot be defeated. (He goes on to argue that nonetheless it is reasonable to regard us having justifiable progress in our knowledge, firstly because we have eliminated mistakes, and secondly because by passing severe tests theories gain corroboration, which is an indicator of verisimilitude. All of this positive work is controversial)
   But he does not quite fall into our category, because he partly (see below) persists in thinking that corroboration, by surviving severe tests, is a justified indicator of truth-likeness (verisimilitude) - that investigators, by claiming to be critical, conjectural, fallibilists, could justify a judgement that their general and low-observability claims were approaching the truth, and hence, for instance, worth relying on to some extent. Putnam (1981) (Feyerabend, and many others - for example Ayer) criticised him for failing to provide any reason for taking severely tested theories seriously. According to these critics, investigators, according to Popper's account, are just playing intellectual games.
   In his (1972), after emphasising that Tp does not lead to truth plain and simple - if it did, then how could famous errors like Newtonian Mechanics have occurred? - he wrote (pp.101-3): "It can hardly be an accident that the theory {Newton's Gravitational theory} predicts these utterly improbable predictions...An accidentally very improbable agreement between a theory and a fact can be interpreted as an indicator that the theory has a (comparatively) high verisimilitude" (italics in original). 'Verisimilitude' means 'nearness to the truth'. He adds, uneasily (p.103): "I do not think that much can be said against this argument, even though I should dislike it being developed into yet another theory of induction".

   Lakatos (1981) clearly, though only in parenthesis, sees the need for (p.119) "some extra-methodological inductive principle". Without it an activity purely based on his principles would be "a mere game ... lighthearted sceptical gambits pursued for intellectual fun". Only with it can the activity become a "more serious fallibilist venture of approximating the Truth about the Universe".

   Putnam (1981) firmly states (p.79) that induction is a 'propensity' that people have, that apparent success strengthens the propensity, and that it cannot be justified.

   Ayer (1990) takes the view that sceptical doubts cannot be resolved, and need to be ignored as sterile.

   Armstrong (1991), showed how inductive generalising can be shown to be a consequence of a principle that improbable coincidences are due to the true existence of a common principle, such as a cause, of some kind.

   Explicit reference to the role of Tp is common. What is interesting about the thinkers quoted above is their explicit acceptance that such a principle may be unjustifiable.  This acceptance is less common, perhaps because it seems defeatist.  Are these philosophers, as they would claim, accepting the way things are, or are they just feebly giving up an essential struggle? The argument of the chapter on quarantining scepticism is that the struggle is not essential, and that these philosophers have correctly seen the writing on the wall.

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