Thursday 28 October 2010

In Our Time: Logic; BBC Radio 4, broadcast 21 October 2010

In Our Time is a programme about the history of ideas chaired by Melvyn Bragg. Last week’s topic was Logic. Melvyn’s guests included: A. C. Grayling, Professor of Philosophy at Birkbeck, University of London; Peter Millican, Gilbert Ryle Fellow at Philosophy at Hertford College at the University of Oxford; Rosanna Keefe, Senior Lecturer in Philosophy at the University of Sheffield.

The programme is usually a leisurely-paced tour down the ages tracing the rise of an idea, philosophical, literary or scientific development, and their impact on our times. To this extent, last week’s discussion was no different. The speakers attempt to boil down a vast body of knowledge to a few bitesize pieces which the general public can comprehend, while Melvyn Bragg’s job is to moderate the discussion (read: ‘herd the speakers’), and steer it towards a conclusion (on rare occasions).

In Our Time rounds off my week nicely, but it can be difficult to concentrate for extended periods of time during the programme, especially if one is unfamiliar with the subject matter.

Logic charted the route from Aristotle, through the swamp of Scholastic philosophy, to modern times, and in particular Gottlob Frege. From the comfort of my armchair, I would have liked to add just a few thoughts of my own where, perhaps, the answers were not entirely to my satisfaction.

Thus, to the question of why the Aristotelian categorical propositions had driven the development of logic and attracted so much attention, I’d say it is because practically all declarative sentences that we use in language can be reduced to one of the four proposition types: A, E, I, O. A proposition of the type A, for example, has the structure: All P are Q, or: All sheep are docile. We can plug into this pattern a sentence like: ‘Politicians promised us the moon,’ simply by paraphrasing it as: ‘All politicians are persons who promised us the moon,’ where ‘politicians’ is ‘All P’, and ‘promised us the moon’ is ‘are Q’, that is ‘are persons who promised us the moon.’ Why should it be useful? Well, it is cool to know that all sentences have been written in a key that fits one of the four patterns.

To the questions of why the medievals were so keen on the development of deductive logic, I’d say it’s because they were looking for an argument to clinch all arguments – an argument which would show incontestably that God exists, without having to refer to any empirical evidence. Chief of those was St Anselm of Canterbury’s ontological argument for the existence of God (roughly: God is perfect. Anything that exists is more perfect than anything that doesn't. Therefore, God exists). The enlightened view today is that such exercises amounted to no more than a load of tosh.

Logic today, the kind I’m interested in anyway, brings together quantification theory, set theory, mathematics and linguistics. It is an open chapter, which is constantly being written, and which in itself is quite annoying, but I’d rather that than the certainties of death and taxes.

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