Destutt de Tracy’s first point is that traditional logic has followed a completely misleading route. The aim of logic should have been to find the ultimate reasons why we sometimes stumble into error and methods for avoiding such errors. After Aristotle had put so much effort in classifying the various species of valid syllogisms, every logician was under the impression that these rather quaint formulas were the essence of logic, although they were sterile and quite useless in producing new truths.
Destutt de Tracy’s second point is that the true source of certainty can actually be found in the two previous parts of his ideology. All human thinking is just sensation, and in a sense, all sensations are as such reliable. Although this might appear rather far-fetched, Destutt de Tracy’s point appears to be simply that when we sense or experience something, we are certainly having that experience and something either outside or inside us is making us experience things in that manner. This means especially that simple sensations of things present are a completely reliable source of knowledge - if we sense red, then we are sensing red and something is making us sense red.
An error comes into the picture only with judgement. There’s no question about it that we sense red and that something makes us see red, but the question is can we say what this red-sensation-making thing is and whether it is even an object outside us or just some hallucination inducing state within us - or, to take another object, if we see a crooked stick, whether this sensation of crookedness is caused by a truly crooked stick or by a straight stick together with the refraction of water.
Now, judgements are also, Destutt de Tracy said, sensations - they are experiences of one idea being connected to another idea. Thus, there is no particular reason why judgements as such couldn’t be as reliable as ordinary sensations. For instance, if we note that a certain sensation must be produced by an external object, because it resists our efforts to change it, we can be fairly certain that this judgement is reliable.
The reason making certain judgements unreliable, Destutt de Tracy suggests, is essentially our bad memory. We have a sensation and are convinced that this sensation resembles sensations we used to have. If our memory of these earlier sensations were faulty, we would then be in error. Since all our general concepts are just abstractions from earlier sensations, according to Destutt de Tracy, this source of error can easily cause much damage in our cognitive state.
“Base your knowledge on present sensations and try to avoid faulty memories” is then the simple answer to most questions of logic - Baconian empiricism is the solution to everything. The only other thing we need to take into account is the role of language, since most of our cognitive processes happen through words. Indeed, when we learn things just through reading - a favourite point of ridicule, of which scholastics used to be accused - we are just having sensations of certain signs, which have the ability to induce in us some ideas, although these ideas might have no resemblance with our direct sensations. Language is thus another possible source of misinformation, but it is also a possible source of correct information, as long as we just know the semantics of the language used.
And this was it! No further methodology is required, Destutt de Tracy appears to say, and a more cynical reader might ask if experience and semantics is truly enough for finding new truths, although they are undoubtedly good tools for avoiding errors.
Apparently just to add some more pages to his book, Destutt de Tracy chose to give a general outline of what his ideology should contain. Despite its supplementary nature, this is by far the most interesting piece of the work. The three books Destutt de Tracy had published thus far formed only the first third of the whole ideology, or in more detail, the part dealing with human cognitive capacities. Even in this part Destutt de Tracy had noticed that human beings had something beyond mere cognition or sensations, namely, active drives, which we sense as volitions. The second part of ideology should then be formed by the study of our volitional side. Since this part of ideology Destutt de Tracy managed to at least partially publish, I shall not handle it now.
The third planned, but never published part should have then dealt with things external to humans. As we saw already with the first part of Ideology, Destutt de Tracy thought our belief in things external to us was based on our volition and especially on the feeling of resistance we have, when we are prevented from getting what we want. This resistance and its various kinds form then in Destutt de Tracy’s view the basis on which physical sciences would have to be founded.
In addition to physical sciences and concrete bodies, this third part of ideology would deal with the abstraction of distance, which we measure with our movement. Thus, we get the ideas of spatial dimensions and shapes, which form the topic of geometry.
Finally, the third part would have to deal with the imaginary world of numbers, which we create from the abstraction of units and an imagined collections of such units. On basis of this simple beginning can be built more and more complex ways to manipulate numbers, which retain their certainty because of their connection with these original notions of unit and addition and because of precision involved in mathematical language. Despite this world of numbers being completely imagined, Destutt de Tracy said, it could be used in real world, just because and when we could find suitable items to take as units.
Next time, we shall see the conclusion to the story of ideology.