Definition of tautology
1. Redundant use of words.
It is tautology to say, "Forward Planning".
2. An expression that features tautology.
The expression "raze to the ground" is a tautology, since the word "raze" includes the notion "to the ground".
3. A statement that is true for all values of its variables.
Given a Boolean A, "A OR (NOT A)" is a tautology.
A tautology can be verified by constructing a truth tree for its negation: if all of the leaf nodes of such truth tree end in X's, then the original (pre-negated) formula is a tautology.
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Both follow from the equivalence theorem and the tautology theorem.
That's the nature of tautologies.
This is one reason why tautologies are important.
I do not think I have ever come across such a fine exercise in tautology in a public document.
We keep getting caught in a huge tautology and I am afraid that this is precisely the economic policy which you support.
But a statement like that is in itself little more than tautology.
And it's not ATMOS-system, that's a tautology.
But, though this might appear a tautology, there is much that can be done by the United Nations to promote a culture of peace in actions taken to promote peace and security.
Could it be that the Help file writer for this feature didn't know either, and made something up that represented a tautology?
In draft guideline 3.1.1, the chapeau and the first line immediately following it were a tautology.