There are then two regions in which this unity is to be realised. These are expressed by the great words, 'the unity of the faith and knowledge of the Son of God.' These words are open to a misunderstanding, as if they referred to a unity as between faith and knowledge; but it is obvious to the slightest reflection that what is meant is the unity of all believers in regard to their faith, and in regard to their knowledge. It is to be noted that the Apostle has just said that there is one faith, now he points to the realisation of that oneness as the very end and goal of all discipline and growth. I suppose that we have to think here of the manifold and sad differences existing in Christian men, in regard to the depth and constancy and formative power of their faith. There are some who have it so strong and vigorous that it is a vision rather than a faith, a trust, deep and firm and settled, to which the present is but the fleeting shadow, and the unseen the eternal and only reality; but, alas! there are others in whom the light of faith burns feebly and flickers. Nor are these differences the attributes of different men, but the same man varies in the power of his faith, and we all of us know what it is to have it sometimes dominant over our whole selves, and sometimes weak and crushed under the weight of earthly passions. To-day we may be all flame, to-morrow all ice. Our faith may seem to us to be strong enough to move mountains, and before an hour is past we may find it, by experience, to be less than a grain of mustard seed. 'Action and reaction are always equal and contrary,' and that law is as true in reference to our present spiritual life as it is true in regard to physical objects. We have, then, the encouragement of such a word as that of our text for looking forward to and straining towards the reversal of these sad alterations in a fixed and continuous faith which should grasp the whole Christ and should always hold Him. There may still be diversities and degrees, but each should have his measure always full. 'Thy Sun shall no more go down'; there will no longer be the contrast between the flashing waters of a flood-tide and the dreary mud-banks disclosed at low water. We shall stand at different points, but the faces of all will be turned to Him who is the Light of all, and every face will shine with the likeness of His, when we see Him as He is. But our text points us to another form of unity--the oneness of the knowledge of the Son of God.