A question on modification of a list via a function invocation

[Steve D'Aprano]

On Wed, 6 Sep 2017 11:02 pm, Stefan Ram wrote:

> Chris Angelico <rosuav at gmail.com> writes:
>>The 'is' operator tests if two things are the same thing.
> 
>       »Roughly speaking, to say of two things that they are
>       identical is nonsense, and to say of one thing that it
>       is identical with itself is to say nothing at all.«
> 
>     Ludwig Wittgenstein, Tractatus Logico-Philosophicus (5.5303)

"Roughly speaking".

But to be more precise, it is meaningful.

"Was that you yourself I saw yesterday walking down the street, or your
doppelgänger?"

Or to put it another way...

Was the person I saw yesterday identical (in the identity sense) to the person I
am speaking to now?

We don't really use "is identical" (in the identity sense) to compare "two
distinct things" versus "one thing" -- we use it to compare two *operands* and
don't know which situation applies until after we get the answer.

If we already knew they were identical, we wouldn't need to ask.

The same applies to when we are making statements rather than asking questions
(making assertions about identity rather than questioning it). The point of
making the assertion is to pass on information that would otherwise by
ambiguous:

"There is that same (identity) cat again (not merely one that looks like it)."



-- 
Steve
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.