The words, rational and rationalize, have nearly opposite meanings.  To be rational is to be sane.  To rationalize is to try to make irrational thinking sound rational.  Sometimes we try to rationalize an insane thought; we try to make it seem to be sane.  It would make more sense to just leave our irrational thoughts behind and escape to reality rather than trying to justify them.

Rationalism

Rationalism is a philosophy that says that it is sane to rationalize.   Yikes!  How did we come to the point where nearly every school teaches it?

The only way to truly be sane is to see reality.  The only way to have any real perception of reality is to have your mind in submission to your spirit and your spirit in submission to the Holy Spirit--which is only available to those who receive the work of Jesus Christ on the cross.  God is always rational.

Rationalism is something quite different from sanity; rationalism is insane.  All the world runs on rationalism.

Rationalism says that the human mind can manufacture knowledge, wisdom, and understanding without the benefit of knowledge or revelation.  That is insane.  Rationalism is simply the justifying of fabrication.  It is legitimizing supposition.  Usually, it is supposition that is carefully phrased to make it seem as if it were sane.

Rationalism is a huge part of all the secularist cults.