Is ZF a hack?: Comparing the complexity of some (formalist interpretations of) foundational systems for mathematics

This paper presents Automath encodings (which are also valid in LF/λP) of various kinds of foundations of mathematics. Then it compares these encodings according to their size, to find out which foundation is the simplest.

The systems analyzed in this way are two kinds of set theory (ZFC and NF), two systems based on Church's higher order logic (Isabelle/Pure and HOL), three kinds of type theory (the calculus of constructions, Luo's extended calculus of constructions, and Martin-Löf's predicative type theory) and one foundation based on category theory.

The conclusions of this paper are that the simplest system is type theory (the calculus of constructions), but that type theories that know about serious mathematics are not simple at all. In that case the set theories are the simplest. If one looks at the number of concepts needed to explain such a system, then higher order logic is the simplest, with twenty-five concepts. On the other side of the scale, category theory is relatively complex, as is Martin-Löf's type theory.

(The full Automath sources of the contexts described in this paper are one the web at http://www.cs.ru.nl/~freek/zfc-etc/.)     

证候存在的逻辑回答

认为存在的就是客观的,包含了自然客观、思维客观和理性客观;把疾病现象和疾病本质划等号,在症状层面规范证候标准,抛弃中医辨证思维,就等于否定中医。物质不能等于客观,不能取代存在。证候属于理性客观,发生于中医学,是中医“阴阳神气”观念临床实在化(还原)的必然。     

On Fork Arrow Logic and its Expressive Power

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Not Everything is Possible

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