In an argument of this sort, a subjective state--the mere
fact that we have a belief or desire--is used as evidence
for the truth of a proposition.
We can see what's wrong with this argument by identifying the
implicit premise. To make this argument stronger, one would have
to accept the premise that whatever I believe or want
to be true is true. That is, subjectivism implicitly assumes
that we are infallible. And of course we aren't.
Subjectivism is not only a way of adopting conclusions
on subjective grounds, but also--and probably more often--a
way of evading conclusions by refusing to believe in them.
Some people have perfected the skill of simply not seeing
what they don't want to see, and most of us indulge in this habit
occasionally. If the habit were put into words, it would take the
form, "I don't want to accept p; therefore, p isn't true." That's