Rationalism is the basis of many of the divisions within the Church. Rationalism caused the disorders of the inquisition and the crusades.  Without rationalism, there would be no denominational Babylon as we see it today.  It is the force that adds to and takes from the Scripture. It is behind every family and church disorder. It is a source of endless torment and suffering.  See The Cult, Dogmatism.

The Bible warns against this:

Numbers 15:39 . . . and that ye seek not after your own heart and your own eyes, after which ye use to go a whoring:

Rom 8:7  because the carnal mind is enmity against God, for it is not subject to the Law of God, neither indeed can it be.

Psalm 53:1 The fool hath said in his heart, There is no God.

Jeremiah 17:9 The heart is deceitful above all things, and desperately wicked: who can know it?

1 Corinthians 2:14 But the natural man does not receive the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.

Proverbs 28:26 He that trusteth in his own heart is a fool: but whoso walks wisely, he shall be delivered.

Jeremiah 23:16 Thus says the LORD of hosts, Hearken not unto the words of the prophets that prophesy unto you: they make you vain: they speak a vision of their own heart, and not out of the mouth of the LORD. They say still unto them that despise me, The LORD hath said, Ye shall have peace; and they say unto every one that walks after the imagination of his own heart, No evil shall come upon you.

James 1:17 Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning.