The heart means love. A good heart means love to the Lord and to the neighbor, while a hard or stony heart means the love of self or the world -- riches and things. When the psalmist asks the Lord to search his heart, he wants the Lord to see what it is that he loves. And we are what we love. What we eat may form our earthly body, but it's only temporary, what we love forms our spiritual body, beautiful or ugly as we have chosen. It's interesting to note that the first multi-cellular motion of our embryo is the pulsating that starts in a twist of blood vessel that is to become our heart, and the last motion of our natural body is our heartbeat. It is there for all of our natural life. And of course there is a beating heart in our spiritual bodies when we come to put them on.

3635. In the human body there are two organs which are the mainsprings of its entire movement, and also of every action and external or purely physical sensation - the heart and the lungs. These two so correspond to the Grand Man or Lord's heaven that celestial angels there constitute one kingdom, and spiritual angels the other, for the Lord's kingdom is celestial and spiritual. The celestial kingdom consists of those who are governed by love to the Lord, the spiritual kingdom of those who are governed by charity towards the neighbour, 2088, 2669, 2715, 2718, 3235, 3246. The heart and its kingdom in man corresponds to celestial angels, the lungs and their kingdom to spiritual ones. Also the angels flow into things belonging to the heart and lungs, so much so that these things receive their being and are kept in being by means of that influx from them. But the correspondence of heart and lungs with the Grand Man will in the Lord's Divine mercy be presented as a separate subject.