Sunday, May 31, 2015

Logic,Computability and Problems with Sets Theory (English)

...Starting with the pioneering but contentious work of Georg Cantor in creating Set Theory arising from questions in harmonic analysis, we discuss Dedekind's construction of real numbers, ordinals and cardinals, and some of the paradoxes that this new way of thinking led to. We also explain how the Schools of Logicism, Intuitionism and Formalism all tried to steer a path around these paradoxes.

...We look at the difficulties and controversy surrounding Cantor's Set theory at the turn of the 20th century, and the Formalist approach to resolving these difficulties. This program of Hilbert was seriously disrupted by Godel's conclusions about Inconsistency of formal systems. Nevertheless, it went on to support the Zermelo-Fraenkel axiomatic approach to sets which we have a quick look at...

...Then we introduce Alan Turing's ideas of computability via Turing machines and some of the consequences.

The lecture closes with a review of historical positions on the contentious idea of completed infinite sets, quoting illustrious mathematicians from Aristotle to A. Robinson, along with G. Cantor himself...

Ниже есть продолжение.

I should qualify this lecture by stating clearly that in fact I don't really ascribe to any of the theories presented here. My objections will be laid out at length in my MathFoundations series. In this video I am mostly overviewing--rather briefly to be sure!-- the standard thinking, even though I have very little sympathy with it.

But it is important to understand this historical period, since it impacts so heavily on the mathematics that we currently believe in, teach and apply to the world. We are part of a trajectory of human thought, and not necessarily on the pinnacle or high point of that trajectory--much as we would like to think so! In particular, there is much to be learnt by a study of the issues here that so captured the imagination of the late 19th century and early 20th century mathematical and philosophical thinkers.

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