What are the differences between わけ and 理由?


It seems that they are often interchangeable.




Introduction:

I think **理由** is used when there is a concrete evidence to provide the
reason. Probably other people also could use the reason(理由） to explain it. On
the other hand, **わけ** is used when you want to provide a reason with your
interpretation. it's not so necessarily for other people use the reason（わけ） to
explain it.

Background and Appendix:

For example, when you feel hungry and you want to eat donuts, you can say
わけがあって、ドーナッツを食べる。(お腹が減って: your interpretation that you are hungry ）

If your stomach is empty, and that condition urges you to eat donuts （胃の中が空で:
probably someone can observe that nothing in the stomach), you can say
理由があって、ドーナッツを食べる。

Or frogs suddenly began falling from the sky. You can say わけがわからない。since there
is nothing seems to carry the frogs in the sky, so it's bizarre. However you
might find the airplane in the sky, but it can be the reason but is not
sufficient to explain the phenomena. You can say 理由がわからない since it's no clear
evidence.

In conclusion:

Yes, I agree with it's interchangeable in some situations as you know. It's
not easy to provide the reason to explain the phenomena so long as I analyzed
the difference.

