Reid on intentionality

Bill Vallicella cites here the Scottish enlightenment philosopher Thomas Reid, saying that Reid already understood that when one thinks of a unicorn one is not thinking of a mental image, but of an animal. Perhaps he is referring to passages such as this one.

[The object of conception] is not the image of an animal—it is an animal. I know
what it is to conceive an image of an animal, and what it is to conceive an
animal… The thing I conceive is a body of a certain figure and colour, having
life and spontaneous motion. The philosopher says, that the idea is an image of
the animal; but that it has neither body, nor colour, nor life, nor spontaneous
motion. This I am not able to comprehend. (Essays on the Intellectual powers
of man, 4.2, 321-2)

Perhaps this is what is driving Bill's argument from the premiss ‘Tom is thinking of something’ to the conclusion ‘Tom’s thinking has an intentional object’? Tom is thinking of unicorn, Tom is thinking of something other than the thought of a unicorn, ergo Tom stands in some 'intentional relation' to some quasi-unicorn, an 'intentional object'.

Sadly for Bill, this will not work. If I am thinking of a unicorn, then I have a thought of a unicorn. Thus the two following propositions are broadly equivalent.

(A) Tom is thinking of a unicorn
(B) Tom has the thought of a unicorn

But this still doesn't get the conclusion that Bill wants, namely

(C) Tom's thinking has an intentional object.

For (B) can be true even though there are no unicorns. The verb phrase 'has the thought of' is intentional. But the verb 'has' on its own is non-intentional. 'Tom's thinking has an intentional object' is inconsistent with 'there are no intentional objects'. As I have argued, we cannot argue without other assumptions from a sentence using an intentional verb, to a sentence using a non-intentional verb.

The confusion probably occurs because of the two grammatical accusatives in sentence (B) above. The first is 'the thought of a unicorn', which is the object of the non-intentional verb 'has'. We cannot have an F without there being an F, and so cannot have the thought of a unicorn without there being a thought of a unicorn. The second is 'a unicorn', which is the object of the verb phrase 'has the thought of'. Seeing that the first accusative has a corresponding logical accusative, we are tempted to assume that the second has also. But the second verb phrase is clearly intentional, and so the existence of its grammatical accusative does not justify the existence of any logical accusative.

The fact that there are two grammatical objects in (B) does not justify the conclusion that there are two logical objects. This only follows if the two corresponding verb phrases are non-intentional. But they are not, and so the conclusion does not follow.

* Essays on the Intellectual Powers of Man, Derek Brookes (ed.), University Park: Pennsylvania State University Press, 1785/2002.

Logic and scientific reasoning

This is a follow-on from my earlier post about whether Aristotle's account of scientific reasoning truly captures what scientific reasoning is. He describes two forms: propter quid where we reason from cause to effect, and quia, where we reason from effect to cause.

Propter quid
Being an A is the cause of anything being a B
This X is an A
This X is a B

Quia
Being an A is the only cause of anything being a B
This X is a B
This X is an A

Neither of these captures the process of geniune scientific reasoning or discovery. In propter quid, the major premiss cannot be known unless the causal connection 'A causes B' has already been established. Since proof of the causal connection is the end-product of scientific reasoning and methodology, rather than the beginning, Aristotle's syllogism captures nothing useful. The same objection applies to the quia form, with the additional objection that the 'only' qualification cannot be established with any certainty at all. Scientific reasoning involves constructing a model of reality that explains the observed effects. It is difficult to establish that such a model is the only one. Ptolemy's model of the solar system (where the earth is at the centre) explained the observations available to ancient scientists. Copernicus' model (sun at the centre, circular orbits) explains the same observations, but in a different way. Kepler's model (sun at the centre, elliptical orbits) is different again. Further changes and refinements to this model continued into the twentieth century. It is difficult to prove that any model is the only explanation of the observed effects.

And in any case, how could such a simple syllogism as Aristotle's capture the essence of what is essentially a complex reasoning process that could take many forms?

See also Thomas Reid on the utility of logic.

"The art of syllogism produced numberless disputes, and numberless sects who
fought against each other with much animosity, without gaining or losing ground,
but did nothing considerable for the benefit of human life. The art of
induction, first delineated by Lord Bacon, produced numberless laboratories and
observatories, in which nature has been put to the question by thousands of
experiments, and forced to confess many of her secrets that before were hid from
mortals: and, by these, arts have been improved, and human knowledge wonderfully
increased.

"In reasoning by syllogism from general principles, we descend to
a conclusion virtually contained in them. The process of induction is more
arduous, being an ascent from particular premises to a general conclusion. The
evidence of such general conclusions is probable only, not demonstrative: but
when the induction is sufficiently copious and carried on according to the rules
of art, it forces conviction no less than demonstration itself does."

On whether 'induction' is any improvement on Aristotelian 'deduction', more later.