My right hand hasn't seen my left hand

[Pavel Pin]

Sidney: What I mean, we got a slippery, dangerous problem here.

J.J: Not we, Sidney. You.

Sidney: Correct me if I'm wrong, J.J. - we! Because if I'm gonna go out on a limb for you, you gotta know what's involved.

J.J: My right hand hasn't seen my left hand in 30 years.

How human hand can see ?

Is it sarcasm involved?

Source: Sweet Smell of Success 1957

 

[natkretep]

Clearly, it is not literal, and I think it is a kind of a joke.

JJ is playing around with Sidney's phrase 'go out on a limb', meaning 'put oneself in a disadvantaged position', but I think JJ picks up 'limb' from the expression which usually means arms or legs (actually the phrase refers to a branch of a tree), and he refers to 'hands', part of one's arms.

The metaphorical use is familiar from the words of Jesus in the Bible ('But when you give to the needy, do not let your left hand know what your right hand is doing', Matthew 6:3). JJ is happy not to know what is involved.