“It is one which gives great pleasure to a home-loving person who finds satisfaction in that which is his own. Often have I seen a householder sitting under its sweet shade, well content. He was conscious of having an argument which answered to all his needs, and which protected him alike from the contradiction of sinners and from the intrusive questioning of the more critical sort of saints. He had such satisfaction as came to Jonah, when the booth he had constructed, with such slight skill as belonged to an itinerant preacher, was covered by the luxuriant gourd vine. Things were not going as he had expected in Nineveh, and current events were discrediting his prophecies, but Jonah ‘rejoiced with great joy over the gourd.’
“I may be pardoned, in treating the circular argument, for deviating, for a moment, from the field of botany into the neighboring field of zoölogy. For after all, the same principles hold good there also, and as we are forming the habit of looking at thought as a kind of plant, we may also consider it as a kind of animal,—let us say, if you please, a goldfish. You have often paused to watch the wonders of marine life as epitomized in a glass globe upon your centre-table. Those who go down to the sea in ships have doubtless seen more of the surface of waters, but they have not the same facilities for looking into its interior life that you have in your aquarium. A school of goldfishes represent for you the finny monsters of the deep. You see the whole world they move in. The encircling glass is the firmament in the midst of the waters. The goldfishes go round and round, and have a very good time, and have many adventures, but they never get out of their crystal firmament. You may leave them for half a day, but when you come back you know just where to find them. An aquarium is a much safer place for goldfishes to swim in than the ocean; to be sure, they do not get on far, but on the other hand they do not get lost, and there are no whales or even herrings, to make them afraid. There is the same advantage in doing our reasoning in a circle. We can keep up an argument much longer when we are operating in friendly waters and are always near our base of supplies. The trouble with thinking straight is, that it is likely to take us too far from home. The first we know we are facing a new issue. From this peril we are saved by the habit of going round and round. He who argues and runs away from the real difficulty lives to argue another day, and the best of it is the argument will be just the same.
“Argumentum ad Hominem. This is a large family, containing many interesting varieties. The ad hominem is of parasitic growth, a sort of logical mistletoe. It grows not out of the nature of things, but of the nature of the particular mind to which it is addressed. In the cultivation of this fallacy it is only necessary to remember that each mind has its weak point. Find out what this weak point is, and drop into it the seed of the appropriate fallacy, and the result will exceed your fondest anticipation.
“Again with the reader’s kind permission, I will stray from the field of botany; this time into that of personal experience. At the risk of falling into obsolete and discredited methods of instruction, I will ask you for the moment to look in and not out.
“Dear Reader, often, when reasoning with yourself, especially about your own conduct, you have found comfort in a syllogism like this:—
I like to do right.
I do what I like.
Therefore, I do what is right.
The conclusion is so satisfactory that you have no heart to look too narrowly at the process by which it is attained. When you do what you like, it is pleasant to think that righteousness is a by-product of your activity. Moreover, there is a native generosity about you which makes you willing to share with others the more lasting benefits which may ensue. You are ready to believe that what is profitable to you must also be profitable to them in the long run,—if not in a material, then in a spiritual way. All the advantage that comes to you is merely temporary and personal. When you have reaped this scanty harvest, you do not begrudge to humanity in general its plentiful gleanings. In your altruistic mood you do not consider too carefully the particular blessing which your action has bestowed on the world; you are content with the thought that it is a good diffused.
“When out of what is in the beginning only a personal gratification there grows a cosmic law, we have the Argumentum ad Hominem. There are few greater pleasures in life than that of having all our preferences justified by our reason. There are some persons who are so susceptible to arguments of this kind that they never suffer from the sensation of having done something wrong,—a sensation which I can assure you is quite disagreeable. They might suspect they had done wrong, were it not that as soon as they begin to reason about it they perceive that all that happened was highly to their credit. The more they think about it, the more pleased they are with themselves. They perceive that their action was much more disinterested than, at the time, they intended. They are like a person who tumbles into the Dead Sea. He can’t go under even if he tries. It is, of course, a matter of specific gravity. When a conscience is of less specific gravity than the moral element into which it is cast, it cannot remain submerged. The fortunate owner of such a conscience watches it with satisfaction when it serenely bobs to the surface; he advertises its superlative excellence,—‘Perfectly Pure! It floats.’
“The great use of the ad hominem argument is like that of certain leguminous plants which enrich the soil by giving to it elements in which it had been previously lacking. After a crop of ad hominem arguments has grown and been turned under, we may expect a rich harvest of more commercially valuable fallacies in the next season. To thus enrich the soil is an evidence of the skill of the culturist.
“Suppose, for example, you were to attempt to implant this proposition in the unprepared mind of an acquaintance, ‘All geese are swans.’ The proposition is not well received. All your friend’s ornithological prejudices are against it. There is no foodstuff to support your theory.