Blessed are the Pure in Heart

"What is it, then, to be pure in heart?"
I answer: it is not necessary to define this purity, or to have in the mind any clear form of it. For even to now perfectly what purity of heart is, were that possible, would not be the same as to be pure in heart.
"How then am I to try to seek such purity? How can I do so without even knowing what it is?"
Though you do not know any definition of purity, you know enough to begin to be pure....
You who seek purity, and would have your fellowmen also seek it, spend not your thoughts and labor on the stony ground of their intellect, endeavoring to explain what purity is. Give to their imagination a picture of the one pure man. Call up their conscience to witness against their own deeds. Urge upon them the grand resolve to be pure.
With the first endeavor of a soul towards it, purity will begin to draw nigh, calling for admittance.

George MacDonald. KNOWING THE HEART OF GOD. Seeking God.