"Our Lord saith that the Kingdom of God is near us. Yea, the Kingdom of God is within us as St Paul saith 'our salvation is nearer than when we believed.' Now we should know in what manner the Kingdom of God is near us. Therefore let us pay diligent attention to the meaning of the words. If I were a king, and did not know it, I should not really be a king. But, if I were fully convinced that I was a king, and all mankind coincided in my belief, and I knew that they shared my conviction, I should indeed be a king, and all the wealth of the king would be mine. But, if one of these three conditions were lacking, I should not really be a king.
"In similar fashion our salvation depends upon our knowing and recognizing the Chief Good which is God Himself. I have a capacity in my soul for taking in God entirely. I am as sure as I live that nothing is so near to me as God. God is nearer to me than I am to myself; my existence depends on the nearness and presence of God... [Man's] happiness increases and diminishes in proportion to the increase and diminution in his knowledge of this. His happiness does not arise from this that God is near him, and in him, and that He possesses God; but from this, that he knows the nearness of God, and loves Him, and is aware that 'the Kingdom of God is near.' So, when I think on God’s Kingdom, I am compelled to be silent because of its immensity, because God’s Kingdom is none other than God Himself with all His riches. God’s Kingdom is no small thing: we may survey in imagination all the worlds of God’s creation, but they are not God’s Kingdom. In whichever soul God’s Kingdom appeareth, and which knoweth God’s Kingdom, that soul needeth no human preaching or instruction; it is taught from within and assured of eternal life. Whoever knows and recognizes how near God’s Kingdom is to him may say with Jacob, 'God is in this place, and I knew it not.'"
From the sermon "The Nearness of the Kingdom"