He thinks that war is a necessary evil.

He is a rationalist, making all decisions based on logic and facts.

I am surprised at the irrationality of this system.

This system is too irrational to understand.

His behavior is illogical and incomprehensible.

His behavior was illogical and I couldn't understand it.

His opinion is always rational.

My personal thought is that everyone should be treated equally.

He values his private life.

He holds a personal grudge against me.