Effect to An argument from Effect to Cause is one in which the existence of an effect is given as a reason to prove a cause that is known to be adequate to produce that effect. Such an argument may only be probable since the same effect may be pro duced by two or more causes, and it approaches to conclusiveness in so far as all the causes but one can be shown not to be operative. Thus, when we argue that it has rained because the streets are wet we use an argument from an effect (the wet street) to a cause (rain), and it is conclusive in so far as we show that no other cause operated which might produce the effect, as for example, a heavy dew, melt ing snow, the sprinkling cart, the bursting of a water main, etc.
The principle relied on in arguments of this kind may be stated as follows: when any cir cumstance is known to be adequate to produce a given effect, that effect having appeared and no other cause having operated to produce it, the effect in question was preceded by that circumstance.
An argument from Testi mony may be regarded as an argument from an effect to a condition, the giving of the testi mony being the effect and the reality of the fact testified to being a more or less probable condition of the effect; in other words we argue that the testimony would not have been given if the fact testified to were not true. The assumption relied on in every argument from testimony is that the witness is trust worthy, and the principle on which we rely is: what a trustworthy witness testifies to is true. An argument from testimony may be stated formally thus: T: A assaulted B; R: Because C, a trustworthy witness, testifies that he saw him do it; P : Because what a trustworthy wit ness testifies to is true. It is assumed both in the courts of justice as well as in the ordi nary affairs of life that a witness is trustworthy unless the contrary is shown, in much the same way that an accused person is presumed to be innocent until he is proved to be guilty, and the burden of showing that he is not trust worthy is usually upon him who asserts his untrustworthiness.
Sign.—An argument from Sign is one in which the fact to be proved and the fact cited as a reason, although not related as cause and effect, are associated through some fact of caus ation, usually as joint effects of a common cause either known or assumed to exist. Thus, when we argue that it will rain because the mercury is falling in the barometer, or that this animal is a ruminant because it is horned, or that Congress is in session because the flag is flying over the Capitol, we use arguments from sign. Arguments from testimony, from cause to effect and from effect to cause, are also sometimes called arguments from sign, but it is convenient to use the term in the sense above indicated. In a wide sense all arguments are
arguments from sign since sign is only another name for evidence. The principle relied on in this argument is usually a law already estab lished by the argument from Example.
Circumstantial this argu ment the reason consists of a number of facts or circumstances any one of which taken by itself may have little evidential force, but which taken together form a body of evidence that is often stronger than the direct testimony of wit nesses. It is in the nature of an argument from cause to effect or from effect to cause or from sign, or it may contain elements of all three. An example of the establishment of a thesis by circumstantial evidence may be taken from al most any criminal trial. In one case the house of a license inspector, who had aroused the hostility of liquor sellers by a strict enforce ment of the law, was wrecked by some ex plosive. Shortly after the explosion, which happened about one o'clock in the morning, marks of footsteps in the fresh snow were found leading from the place of the explosion to one of the hotels, not by the most direct route, but circuitously around a block and through a back alley to the rear entrance of the hotel. In one of the rooms was found a pair of boots which coincided with the footmarks made in the snow, and under the mattress of the bed there were two sticks of dynamite and an unused dynamite fuse. The owner of the boots who occupied that room was unable to give any satisfactory explanation of these facts, and he was tried and convicted of the crime. The reason in an argument of this kind is seldom stated in full. The advocate relies on an implied assumption that the facts stated as evidence cannot be accounted for in any rea sonable way except on the truth of the thesis. The proof of incriminating facts has the effect of shifting upon the accused the burden of showing that the facts can be explained or accounted for in some other way. The prin ciple upon which an argument of this kind is based may be stated as follows: "Every thesis that is exclusively sufficient to explain a given set of facts is true,' and the whole argument may be stated formally as follows: T: A caused the death of B; R: Because that thesis is exclusively sufficient to explain the facts A, B, C, D, etc.; P: Every thesis that is exclu sively sufficient to explain a given set of facts is true. The same kind of argument is em ployed in a great variety of other cases, as for example in proving the existence of a glacial epoch in prehistoric times, or that Sir Philip Francis wrote the letters of Junius.