Titus 1:15

Titus 1:15 To the pure, all things are pure, but to the defiled and unbelieving, nothing is pure; but both their minds and their consciences are defiled. 16 They profess to know God, but they deny him by their works. They are detestable, disobedient, unfit for any good work.

The false-teacher types that Paul describes from v. 10 really are destructive to families and the church. So much, that Paul ends with this description of the defiled-ness of their minds and consciences. It is by their works - the stuff they do (including their teaching) that they prove that they really deny God. These are the opposites of one who simply trusts God and His word. 

May this be true of me: that I would be counted in "the pure" of this verse - and so see things as they are - and not be defiled and unbelieving - and so seeing evil where there is none. Let me know God - not deny him by my works. Do my works show that I know God - show my faith - "justify" my claims to have true faith. I want to watch my life and see that my works do that more and more. May the Lord help me.