Any problem is concerned with the mind, but what do minds make a decision on?
Here we show that there are three conditions for the mind to make a certain
answer. We found that some difficulties in physics and mathematics are in fact
introduced by infinity, which can not be rightly expressed by minds. Based on
this point, we suggest a general observation system, where we use region (a
type of infinity) to substitute for infinitesimal (another type of infinity)
and thus get a consistent image with the mind. Furthermore, we declare that
without world pictures we can never have ideas to any expressive events, which
is the primary condition for a wave function like mind to collapse to a series
of numbers. A following observation by expanding algorithm brings the final
collapse: classifying the numbers and coming up with a certain yes or no
answer.