John 7:17
If any man’s will is to do his will, he shall know whether the teaching is from God or whether I am speaking on my own authority.
For Jews, truth or “emeth” was more than a philosophical abstraction. It was something solid, something you could sink your teeth into. It might be defined, said C.S. Lewis as “that which holds water.” There is a sense of solid, practical, no-nonsense sturdiness to the Jewish conception of truth. “Taste and see that the Lord is good!” is a very typically Jewish way of talking about the truth and goodness of God. Catholic faith shares in this. Jesus is the truth and his word is the truth, not in some airy theoretical sense, but in a real-life nuts and bolts way. That is why Jesus says, “The way to know whether what I say is true is to do it.” Taste and see.