19. It is with charity and faith in man precisely as it is with the motion of the heart called systole (contraction) and diastole (dilation), and the motion of the lungs called respiration. There is, moreover, a complete correspondence of these organs with the will and the understanding of man, and thus with charity and faith. Therefore, the will and its affection are meant in the Word by the heart, and the understanding and its thought by the soul (anima), and also by spirit (spiritus). Hence, to yield up the soul means to be no longer alive and to give up the spirit means no longer to breathe. From this it follows that there cannot be faith without charity, nor charity without faith; and that faith without charity is like the breathing of the lungs without the heart, which cannot take place in any living creature but only in an automaton; and that charity without faith is like a heart without the lungs, from which no sense of living is perceived: consequently, that charity performs uses by means of faith as the heart performs its functions by means of the lungs.
So great indeed is the likeness between the heart and charity, and between the lungs and faith, that in the spiritual world it is known solely by every one's breathing what is the nature of his faith, and by the beat of his heart what is the nature of his charity. For angels and spirits live by the heart's action and by respiration just as men do; and hence it is that they, like men in the world, feel, think, act and speak.