399. (1) Love or the will is a person's very life. This follows from the correspondence of the heart with the will, as discussed in nos. 378-381 above; for as the heart functions in the body, so the will does in the mind. Moreover, as all the constituents of the body depend for their existence and motion on the heart, so all the constituents of the mind depend for their existence and life on the will. We say on the will, but we mean on love, because the will is the recipient vessel of love, and love is life itself (see nos. 1-3 above), and love which is life itself comes from the Lord alone.
It can be known from the heart and its extension throughout the body by means of the arteries and veins that love or the will is a person's life, because things that correspond to each other function similarly, with the difference that one is natural and the other spiritual.
[2] How the heart functions in the body is apparent from the study of anatomy, as for example, that everything is alive or is responsive to life where the heart operates through vessels issuing from it, and that everything is lifeless where the heart does not operate through its vessels. Moreover, the heart is also the first and last organ to function in the body. Its being the first is clear from fetuses, and its being the last is clear from people dying; and that it functions without the concomitant operation of the lungs is clear from cases of suffocation and fainting.
It can be seen from this that as the subsidiary life of the body depends on the heart alone, so likewise does the life of the mind depend on the will alone, and that the will likewise continues to live if thought ceases, as the heart does if respiration ceases - as is also apparent from fetuses, from people dying, and from cases of suffocation and fainting.
It follows from this that love or the will is a person's very life.
