Extraterrestrial life

[Emsworth]

Do I believe that it exists? No
Do I disbelieve that it exists? No

[Emsworth]

If the second is true, it is my belief that life is such an astounding
accident, requiring such perfect arrangements of chemicals to arise
under such perfect environmental circumstances, that there is no other
life anywhere else, let alone life intelligent enough to travel across
the vast expanse of space to visit us.

Perhaps not. The number of stars in the universe, and the number of planets, is astonishingly enormous.

The Drake equation, with even somewhat conservative estimates, would yield a relatively large number of planets with intelligent life, and an even larger number of planets on which life arose. Drake himself estimates 10,000 intelligent civilizations.

[Emsworth]

Drake fails to take into account the mind-boggling complexity of even the simplest possible lifeforms.

Actually, he does: there is a parameter in the equation f_l that estimates the fraction of planets suitable for life that develop life.

[Emsworth]

We might be talking about a species that breaths nitrogen, for example

Nitrogen gas (N2) would have zero value for respiration.  The Nitrogen triple bond takes enormous amounts of energy to break.

But why should our experience as to the capabilities of beings on the Earth constrain the capabilities of hypothetical creatures from other planets?

[Emsworth]

Nitrogen takes huge amounts of energy to break, whether you are Carbon, Silicon, or Marshmellow-based life.  The laws of chemistry don't change just because you're on another planet.

The laws of chemistry, yes: but such is not necessarily the case with the principles of biology. We cannot assume that our observations of the abilities of living beings on the Earth will apply throughout the universe.