READING: I §4 4
Back to reading:
I §4 3
begin quote ita"
CHAPTER I [:] Notions from Set Theory [...] §4. FINITE AND INFINITE SETS. "end quote
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Please read these notes from the beginning to here.
THE if AND only if PARTS OF if and only if
I would like to explain the if and only if parts of an if and only if statement. However, I would like to do this without letters because I do not want the symbols to have an assumed order - as would be the case if we use A and B. Therefore, I will use and .
Statements to be proved will often be in the form if and only if . Recall from the first reading of §1 that the words if and only if can be replaced by a double arrow which should be read in both directions, and each direction is a material implication.