Is a Good action done for an evil reason - befitting a good alignment shift?

Following the same logic, does an evil act for good reason befit an Evil shift?

Lawful/Chaotic?

Entirely circumstantial; there is no general rule regarding this.

AFAIK good and evil are real and quantifiable in FR. Generally speaking, this means that any bad thing you do gives your soul a 'taint', and any good thing the opposite.

Thusly, I guess even if you do a good thing for the wrong reasons it's still a good act, and vice versa. Such is how fallen paladins come about sometimes. They can't -afford- to be deceived into doing bad acts which I guess is what makes them so grumpy :)