[pjscott]

In perception, yes, but not in reality. If you want to be alive tomorrow, jumping off a tall building will be irrational even if you think it's the last step in a convoluted ritual to grant yourself immortality. That's an exaggerated example, but the principle holds in general: people's desires may differ, but the rationality of any actions taken in the pursuit of those desires is something you can evaluate objectively, at least in principle.

[Klinky]

What about jumping off a building with a parachute or because it's on fire?

I think real life contains many situations where the most rational situation isn't always clear.

[pjscott]

In that case, there is a rational answer; that it's hard to figure out in a hurry doesn't make it subjective.

[Klinky]

I am not sure there is a rational answer when it comes to possibly jumping from a building and breaking your legs or maybe even dying versus staying in the building and possibly dying from smoke inhalation or burning to death. It would be very hard, even in hindsight to figure out what was the more rational decision.

If you want technological examples, say someone calls someone else irrational for basing their website off PHP instead of Ruby. Someone calls the printer industry irrational for making it cheaper to buy a new printer than to buy ink cartridges or that someone buys a new computer because their computer is infested with malware instead of re-installing Windows. You could say those are irrational choices, but the people who are making those choices probably have reasons for doing so which may make sense to them. The person with PHP may not know Ruby and would have to invest significant time in learning it. The printer companies bottom line will make their decision rational to many. The person buying a new computer may not have the skills to perform the task, the local computer shop wants hundreds of dollars to do the work & the computer is old.

So on the surface we say "that's irrational", but then later after learning more, maybe our opinion would change to "that's actually rational".

Also this does bring up the point that we often have to make a choice on what to do without the power of hindsight or with incomplete data. This can make our choices look irrational to those who are not in our shoes.