On p22 in The Big Questions by Solomon:
A tautology is a trivially true statement. Some examples:
A man is free if he is free.
You can't know anything unless you know something.
I wouldn't be here if I hadn't arrived.
Are these four statements all tautologies?
Business is business.
Boys will be boys.
"A rose is a rose is a rose." (Gertrude Stein)
"Become who you are." (Friedrich Nietzsche)
"Business is business" means in order for a business to be successful it is necessary to do things that may hurt or upset people.
"Boys will be boys" means being rough or noisy is part of the male character.
(Both of the above are highly dubious claims: The first may be true to some degree, but suggests that working towards being successful makes it "ok" to harm others, which is highly questionable. The second is, at best, perpetuating stereotypes that are only true on average, that are learnt behaviour or that aren't accurate at all, and at worst, is used to excuse harmful behaviour, e.g. abuse, neglect or violence, just because it was perpetrated by a boy or man. But that's an aside.)
"Rose is a rose is a rose is a rose" is part of a poem to express that simply using the name of a thing already invokes the imagery and emotions associated with it.
"Become who you are" cannot be a tautology, because it's a command, not a statement, but it may seem paradoxical, in the sense that you already are who you are. Although it actually seems to mean that you should "be(come) your best self" by reflecting on your short-comings and overcoming your flaws.
So, while these may seem like tautologies when considering the words as written, the deeper meanings behind these sayings are clearly not tautological.
A man is free if he is free.
A tautology of the form: P→P
You can't know anything unless you know something.
Suppose Kx means 'x is a known proposition' and we're just talking about everything, this says: (∀x¬Kx ∨ ∃xKx) which with quantifiers exchanged amounts to (¬∃xKx ∨ ∃xKx) A tautology.
I wouldn't be here if I hadn't arrived.
A tautology like the first, without mincing the meaning too badly, this says: (¬P→¬P) (it might have some tensed/modal meaning too, but then it won't be a tautology.
Business is business.
Kind of a weird thing to consider. It might mean P therefore P. It might mean: ∀x(Bx→(x=x)) (where B means 'x is business' this says if anything is business it is identical to itself.)
It might mean: ∀x(Bx→Bx) with a meaning analogous to the first tautology again. The problem here is that we're considering an idiomatic expression, something like an exclamation rather than a statement (the truth-evaluable stuff of logic.) Then it's not a tautology.
Boys will be boys.
Again an idiom, or something. Strictly parsed it might be like, where Bx means 'x is a boy', t and t' are times, and x<y is a relation and means 'x is later than y' and Lxy is a relation and means 'x is located at y', and finally we're talking about everything:
∀x∀y(x=t ∧ By ∧ Lyt → ∃z(z=t' ∧ t'<t ∧ Lyz))
Or something funky like that, without modifying the logic too much. Not a tautology in quantified predicate logic. In tense logic it's not good either, basically: p→F(p) (Being a boy implies future boyhood) Kind of confusing overall.
"A rose is a rose is a rose." (Gertrude Stein)
Where Rx means 'x is a rose', and we're talking about everything: ∃x∃y∃z(Rx ∧ Ry ∧ Rz ∧ x=y ∧ y=z)
Not a tautology. Charitably we might wonder if it means everything is identical to itself, in which case it is a tautology, one of the laws of thought.
"Become who you are." (Friedrich Nietzsche)
An imperative, not a truth evaluable statement.
Final thoughts: Forgetting about the little semantics I've done for the logical expressions, just look at the expressions here and think: is there an interpretation (and domain) for these symbols that could make them false? A tautology's truth will come from the fixed logical meanings of the connectives or quantifiers or identity. Hence logical truth.
There are two approaches to your question regarding tautolgies:
Evaluating a statement literally (by syntax): Business is business -> Business = business. Syntactically or literally tautological
Evaluating a statement by semantics (symbolic or metaphoric)
"Business is business" means in order for a business to be successful it is necessary to do things that may hurt or upset people.
Semantically (metaphoric or symbolic), not a tautology.
Special thanks to Michael Carey at Math SE and all the other nice people who answered and commented.
