Back to the map.
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.