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.

681. What celestial and spiritual food is can be seen best of all in the next life. The life of angels and spirits is not maintained by any food like that found in the world but 'by every word that goes out of the mouth of the Lord', as the Lord Himself teaches in Matthew 4:4. The situation is this: The Lord alone is the life of all. From Him comes every single thing that angels and spirits think, say, and do. This applies not only to angels and good spirits but also to evil spirits. The reason the latter speak and do things that are evil is that they receive and corrupt in this way all goods and truths that are the Lord's. For as is the form of the recipient so is the nature of reception and affection. This may be compared to different objects which receive the sun-light. According to their form and according to the arrangement and delimitation of their parts, some convert the rays of light received into unpleasant and hideous colours, while other objects convert them into pleasing and beautiful colours. In such a manner the whole of heaven and the whole of the world of spirits derive their life from everything that goes out of the Lord's mouth, and from this each individual has his life. Indeed this applies not only to heaven and the world of spirits but also to the whole human race. I realize that people are not going to believe it, but I can positively declare from years of uninterrupted personal experience that this is utterly true. Evil spirits in the world of spirits however refuse to believe that it is so, and consequently they have been shown it convincingly time and again until they have grudgingly confessed it to be true. If angels, spirits, and men were deprived of this food they would instantly breathe their last.