3. Therefore it is followed by B.
The advocates of a high protective tariff argue that if the tariff is removed financial disaster will overwhelm the country. They support this contention by showing that the large manufacturing industries are now able to sell their products at a reasonable price; import duties prevent foreign manufacturers from shipping their goods into this country and selling them much cheaper than our manufacturers can make them. But if the tariff is removed foreign made goods will drive out American made goods, as the foreign goods can be sold much cheaper. Therefore factories and mills must cease operations because there will be no demand for their products. Workmen will be thrown out of employment and capital will be idle. Starvation will overtake the working man and financial ruin will overtake the business man. This is a typical example of an argument from cause to effect. The operation of the cause (the removal of the protective tariff) will produce the alleged effect (industrial disaster). This argument appears to be valid, but an equally plausible argument may be constructed against protection. We must, therefore, look at the foundations of each argument for the purpose of determining its validity. As in the case of argument from effect to cause we must exercise sound judgment in applying certain requirements to each particular argument. An argument from cause to effect must conform to the following requirements:
1. The observed cause must be sufficient to produce the alleged effect.
This requirement implies absolute sufficiency of cause, not probable sufficiency. Habitual inattention to business or professional duties is a sure cause for failure. Habitual drunkenness is a sure cause for ill health. Being run over by a locomotive is a sure cause of death. There may be some exceptions to the above general rules, but the certainty of the effect following the cause is so great that for all practical purposes we may rely absolutely upon the sequence.
2. When past experience is invoked it must show that the alleged effect has always followed the observed cause.
An observed cause may possibly have an alleged effect even though there is not one chance in a thousand that it will have this effect. No valid argument can be constructed upon such a chance. In pure science this rule is absolute. A combination of the same chemicals under the same conditions always produces the same effect. The bringing of a magnet near a piece of steel always results in the same effect so far as the force which one exerts upon the other is concerned. When we depart from the realm of exact science the working out of the rule becomes less certain. Nevertheless, if human experience has sanctioned the adoption of the rule we may rely upon it even though there are exceptions. A rise in the tax rate is always followed by more revenue to the government. A scarcity in the supply of iron is always followed by a rise in the price. A drouth in the wheat belt is always followed by an increase in the price of flour. There may be exceptions to these examples, but the exceptions are so few and the number of instances supporting the rule is so great that we feel safe in relying upon it. It is this kind of certainty, rather than the absolute certainty of science, which argumentation demands.
3. No force must intervene to prevent the observed cause from operating to produce the alleged effect.
A drouth in the wheat belt naturally causes an advance in the price of flour. Past experience has proved this to be the case, and, furthermore, the cause is adequate to produce the alleged effect. Nevertheless, a lowering of the duty on wheat might permit wheat from foreign countries to be imported in such quantities that there would be no rise in the price of flour. The lowering of the duty on wheat would be another force intervening to prevent the observed cause (the drouth in the wheat belt) from producing the alleged effect (the rise in the price of flour). Therefore we must always examine the circumstances of each case to determine whether there are any forces at work which will prevent the observed cause from producing the alleged effect.
4. The conclusion established should be verified by positive evidence wherever possible.
After all the other tests have been satisfied the argument from cause to effect may be established or overthrown by the production of positive evidence. A disappears and B is accused of his murder. A perfect case is made out and B is convicted and sentenced to death. Then A suddenly appears. The innocence of B is effectively established. Cases of this kind are not unknown to the criminal law, though unfortunately the missing man is usually discovered after his supposed murderer has been put to death. This illustration suggests that too much care cannot be exercised in substantiating an argument from cause to effect.