1. ## no toads are not green

An immediate inference is an inference which can be made from only one statement or proposition. [1] For instance, from the statement "All toads are green." we can make the immediate inference that "No toads are not green." There are a number of immediate inferences which can validly be made using logical operations, the result of which is a logically equivalent statement form to the given statement. There are also invalid immediate inferences which are syllogistic fallacies.

Could you explain " No toads are not green" in easy way?

2. ## Re: no toads are not green

Toads whose colour is something other than green do not exist. Or to put it succinctly "all toads are green."

3. ## Re: no toads are not green

For all X, there does not exist X such that X is a toad and X is not green.
Hence, for all X, if X is a toad, X is green.

But simpler:
[not-A -> not-B <==> B -> A] (transposition rule)
(P → Q) Q → ¬ P)
http://en.wikipedia.org/wiki/Transposition_(logic)

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