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this is a cool video. dr. richard feynman, one of the most important physicists of the 20th century, was a great speaker. as a professor, he communicated a passion for physics that it's difficult to emulate. here he improvises (to an audience of freshmen at cornell university) the difference between mathematics and physics.

i take issue with feynman's presentation of mathematics:

... the mathematicians only are dealing with the structure of the reasoning and they don't care what they're talking of (0.23) ... they don't even need to know what they're talking about...what?

mathematicians don't believe their hypotheses are beyond falsification (nothing is better at destroying a hypothesis than a valid counter). i have no idea of what dr. feynman means when he explains:

... if you state the axioms ... if you say such and such are so, and such and such are so, what then? (0.38) then the logic can be carried out withoutwhatknowing what the words such and such mean...(0:45)

*words*is he referring to?

first, axioms can be, 1) logical and 2) non-logical.

1) ∃x ∀y ∼(y∈x), zermelo frank's empty set.

2) (xy)z=x(yz) = xyz (for any x, y, z), (associative property in algebra).

second, mathematicians deal with symbols, not words (unless feynman means words=symbols). that doesn't suggest mathematicians don't have an "idea" of what they're doing.

what's an "idea" in mathematics? i don't know exactly, but for sure, an "idea" doesn't have to have a string of words in it. here are some examples: 1- a music phrase, 2- an image (not an idea?), 3- a potential ingredient for my soup (i intend it as flavor), 4- a strategy of reductio for a particular logical problem.

then dr. feynman adds: "... if the statements about the axiom a carefully formulated and complete enough...

*it's not necessary to known the meaning of these words."*

is dr. feynman protesting the truth-preserving qualities of deduction?

all men are immortal

socrates is a man

therefore, socrates is immortal.

granted, the internal structure of deduction is what makes the unsound argument above valid. it isn't a problem of mathematics that deduction is isolated from physical laws. feynman should applaud that deduction is protected from the ebb & flow of reality!

i take issue with this characterization of mathematicians:

... mathematicians prepare abstract reasoning that's ready to be used if you only had a set of axioms about the real world... (1:26)without axiomatics you would not have mathematics. are we not in agreement that math is deductive? is so, where do you expect math to mine from?

it is as if feynman resents mathematics's deductive exceptionality, a sort of independence from the "real world" (it's not true that all math is strictly insulated from reality. math begins as a practical science):

... you have to have a sense of the connection of the words (he definitely means symbols) with the real world (1:51) ...what about quantum mechanics? i don't believe one needs to translate schrÃ¶edinger's equation into into --never mind english-- any language. math's symbolic language is universal.into english??

at some point feynman realizes that he's bending the discussion too much towards physics (by 3:37):

... and later on always turns out that the poor physicist has to come by, excuse me, when you wanted to tell me about the four dimensions ... (audience laughs).i love feynman.