377. (iii) Charity alone does not produce good deeds, much less does faith alone, but charity and faith together do.
This is because charity without faith is not charity, neither is faith without charity faith, as was shown above (355-361). Therefore charity by itself does not exist, neither does faith by itself; hence it cannot be said either that charity produces some good deeds by itself, nor that faith does by itself. This is similar to the case of the will and the understanding. The will does not exist by itself, so neither does it produce anything; nor does the understanding exist by itself, or produce anything. Everything that is produced comes from both acting together, and is the product of the understanding activated by the will. The reason why this is similar is that the will is the dwellingplace of charity, and the understanding is that of faith. Faith alone is said to be much less productive, because faith is truth, and its function is to create truths, and these enlighten charity and its exercise. The Lord teaches about this enlightenment when He said:
He who does the truth comes to the light, so that his deeds may be made apparent, since they are done in God. John 3:21.
When therefore a person does good deeds in accordance with truths, he does them in light, that is to say, intelligently and wisely.
 The linking of charity and faith is like a marriage between husband and wife. All natural offspring are born of the husband as father and the wife as mother. Likewise all spiritual offspring are born of charity as father and faith as mother; and these are items of knowledge about good and truth. These enable us to recognise the parentage of spiritual families. In the Word too husband and father mean in the spiritual sense the good of charity, wife and mother mean the truth of faith. From this it is plain too that neither charity alone nor faith alone can produce good deeds, just as neither a husband alone nor a wife alone can produce any offspring. The truths of faith not only throw light on charity, they also give it its quality and, moreover, nourish it. Therefore a person who possesses charity and not the truths of faith is like one walking in a garden by night, and snatching fruit from the trees without knowing whether they are good or bad to use. Since the truths of faith not only throw light on charity, but also give it its quality, as said above, it follows that charity without the truths of faith is like a fruit with no juice in it, such as a dried fig or a grape after the wine has been pressed out of it. Since truths nourish faith, as was also said above, it follows that if charity is deprived of the truths of faith, it gets no more nourishment than a person does from eating toasted bread and drinking dirty water from a pool.