What's the difference between からには, 以上, and 上は?

Question

I know all three mean "since that..", "now that..", "So long as...." etc. I have trouble understanding the difference between these three. I was wondering in what scenario would I use these 3 grammar points. Is one more formal than the other? The only thing I can see is that both からには and 上は are used for only verbs and 以上 can be used for nouns.

Answer 1

First, 上は is less common than からには and 以上. I rarely hear 上は of this usage, except the fixed phrase かくなる上は.

In most cases からには and 以上 are interchangeable if used after verbs.

But there could be a difference. By googling I found this paper discussing the difference.

Let me quote the conclusion:

Ⅰ. 「からには」構文の条件節は確定的事態（是、否）を要求するのに対して、「以上」構文の条件節は確定的事態（是、否）でも仮定的事態でも（是、否）可能である。さらに、両者の本質的な違いは前件にナイ形が用いられるか否かではなく、確定的事態であるか否かにある。

Ⅱ. 「以上」構文は常に対照的含意を含むのに対し、「からには」構文は「以上」構文と置き換えられる場合のみ、対照的含意を含む。

Conclusion Ⅰ says that からには can take only facts but 以上 can take assumptions as well.

For example (quoted from the above paper):

おまえがいつまでも嘘をつく以上、私はおまえに会いたくないね

As long as you keep lying, I don't want to see you.

Here, 以上 can mean "if", "provided that" or "as long as" but からには can't. If you use からには it would be:

おまえがいつまでも嘘をつくからには、私はおまえに会いたくないね

Because you keep lying, I don't want to see you.

Conclusion Ⅱ says that 以上 always implies a contrastive meaning (?) at the same time, but からには not always.

For example,

おまえがいつまでも嘘をつく以上、私はおまえに会いたくないね

As long as you keep lying, I don't want to see you.

implies that

If you stop lying, I could see you.

But the following

映画俳優の卵であるからには、これまた人並以上の美貌を備えていた。

Since that he was a movie actor in the making, he was also equipped with better look than ordinary.

doesn't mean "If he isn't a movie actor in the making, he is not so good-looking", so we cannot change からには to 以上.