It is obvious that the sphere of conjugial love makes one with the reproductive sphere. For reproduction is the end in view, and conjugial love is the intermediate cause by means of which it is realised; and end and cause act together in realising their effects and in these, because they are one and the same. It is also obvious that the sphere of the love of children makes one with the sphere of the protection of what is procreated, because it is an end which proceeds from the previous end, procreation; and the love of children is its intermediate cause by means of which it operates. Ends advance in a series one after another; and as they advance the last end becomes the first, and so on up to the final stage, in which they stop or cease to exist. (More on this subject will be found in the explanation of point xii [400]).