## Why must the sentence form of a valid argument be tautological?

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I was thinking along the lines of the obvious, such as when found tautological the form must have been valid but I'm sure there is a more in-depth explanation that I can't reach.

Question was closed 2016-02-05T19:27:09.350

2Could you please add some background information: What is the sentence form of an argument, what is a tautological sentence form? Can you give an example, thanks. – Jo Wehler – 2016-02-01T06:22:47.830