“Senseless” and “irrelevant” synonyms of “unreasonable”

Question

Aren't "senseless" and "irrelevant" synonyms of "unreasonable"?

This question is related to:

• What does it mean when someone calls himself “non sequitur”?
• comments to to my answer to Is there a better noun form of “unreasonable” than “unreasonableness?”

Is not “unreasonable” synonym to “senseless” and “irrelevant”?

Update:
Thanks for answers. I still did not grasp the definitions well.

Is the behavior of Grigori Perelman,
insistingly rejecting intrusions into his private life,
for example, like making a show of him by awarding him a $million,
is seen as non sequitur, unreasonable or senseless
in the eyes of general public and organizers of shows around mathematical sciences?

Answer 1

For purposes of illustration: suppose you're having a discussion, say, about English grammar, and the other person says:

..."I know you've brought many proofs for your opinion, and I know that my way can lead to ambiguities in writing. Still, though, I insist that you are wrong." - then he's being unreasonable.

..."Argle-bargle-fargle!" - then he's being senseless.

..."Look! Ponies!" - then what he's saying is irrelevant.

Answer 2

Those words are not synonyms.

Unreasonable means:

• not guided by or based on good sense
• beyond the limits of acceptability or fairness

Senseless means:

• (referred to a person) unconscious
• without discernible meaning or purpose

Irrelevant means "not connected with or relevant to something".

Your requests are unreasonable.
She has been left senseless, in the middle of the street.
What you are saying is irrelevant; the incident would have happened even if you would have been arrived 10 minutes before.

_{[Reference: the New Oxford American Dictionary.]}

Answer 3

Those words are not related. If they all apply equally well in a situation, it still doesn't make them synonyms. They're entirely unrelated facets of the situation. They're also subjective opinion words. If someone unjustly used all three of these words to insult someone else. Does it make those words a synonym for "insult"?