What does Christ say in the context? He tells the secret of His power. 'I, by the Spirit of God, cast out demons.' And then He goes on to speak about a conflict that He wages with a strong man; and about His binding the strong man, and spoiling his house. All which, being turned into modern language, is just this, that the Lord, by His incarnation, life, death, resurrection, ascension, and government at the right hand of God, has broken the powers of evil in their central hold. He has crushed the serpent's head; and though He may still, as Milton puts it, 'swinge the scaly horror of his folded tail,' it is but the flurries of the dying brute. The conquering heel is firm on his head. So, brethren, evil is conquered, and Christ is the Conqueror; and by His work in life and death He has delivered them that were held captive of the devil. And you and I may, if we will, pass into 'the liberty wherewith Christ has made us free.'
That is the only explanation of Him--in His person, in His character, in His work, and in the effects of that work in the world--that covers all the facts, and will hold water. All others fail, and they mostly fail by boldly eliminating the very facts that need to be accounted for. Let us rather look to Him, thankful that our Brother has conquered; and let us put our trust in that Saviour. For, if His explanation is true, then a very solemn personal consideration arises for each of us, 'If I, by the Spirit of God, cast out demons, then the Kingdom of God is come unto you,' it stands beside us; it calls for our obedience. Jesus Christ, and Jesus Christ alone, can cast the evils out of our natures. It is the Incarnate Christ, the Divine Christ, the crucified Christ, the ascended Christ, the indwelling Christ, who will so fill our hearts that there shall be no aching voids there to invite the return of the expelled tyrants. If any other reformation pass upon us than the thorough one of receiving Him by faith into our hearts, then, though they may be swept and garnished, they will be empty; and the demons will come back. With Jesus inside--they will be outside.
'... Make the tree good, and his fruit good....' --MATT. xii. 33.
In this Gospel we find that our Lord twice uses this image of a tree and its fruit. In the Sermon on the Mount He applies it as a test to false teachers, who hide, beneath the wool of the sheep's clothing, the fangs and paws of ravening wolves. He says, 'By their deeds ye shall know them; for as is the tree so is its fruit.' That is a rough and ready test, which applies rather to the teacher than to his doctrine, but it applies, to some extent, to the doctrine too, on the hypothesis that the teacher's life fairly represents it. Of course, it is not the only thing that we have to take into account; but it may prick many a bladder, and unmask many an error, and it is the way by which the masses generally judge of systems and of their apostles. A saintly life has more power than dusty volumes of controversy.