EFFECT-TO-CAUSE Arg.

The word consequence can mean:

— Effect, referring to a causal, cause-effect relationship, see causality.
— Consequent, referring to a logical, antecedent-consequent relationship, see connectives (§Implication)

1. Effect-to-Cause Argument

Other expressions can also be used as well, such as argument by the effect, or from the effect to the cause, see also a priori, a posteriori.
The effect-to-cause argument works backwards from the effect to its cause. Data is considered to be the effect of a hypothetical cause, which that can be reconstructed based on the data combined with a known causal relationship between this type of fact and its cause.

You have a fever, therefore you have an infection

— Argument: A confirmed fact t, the patient’s temperature. This fact t belongs to the category of facts or events T, “having a temperature”, as defined by medicine. This is a categorisation process.
— Causal law: There is a known causal law linking I-facts “having an infection” to T-facts, “having a temperature.”
— Conclusion: t has a I-type cause, an infection, and the patient should be treated accordingly.

This corresponds to the diagnostic process. One might speak of diagnostic reasoning, a type of abduction.

The effect (the temperature) is the natural sign of the cause. These natural, palpable, effects provide a basis for argument from natural signs:

Look! The ashes are still hot, th a fire must have occurred recently. They cannot be very far away.

In the field of ​​socio-political decision-making, the argument by consequences corresponds to the pragmatic argumentation, which transfers the positive or negative evaluation of the effects of a proposed measure to the measure itself.

The pathetic fallacy is a type of pragmatic argument that goes from the premise that « Rain would ruin our party » to the conclusion, « So, it won’t rain”, as if one’s wishes could influence the natural course of events.

2. Arguments by the Identity of the Consequences

The same type of argument applies to deductions made from the implied meaning of words, as an appeal to the sense of semantic coherence or logical consistency:

Topos: “Another topic consists of concluding the identity of precedents from the identity of results.”
Instance: “There is as much impiety in asserting that the gods are born as in saying that they die; for either way the result is that at some time or other they did not exist” (Aristotle, Rhet. II, 23, 1399b5; F. pp. 313-315).

 If the reason for banning marijuana is that it causes a loss of control, then all substances that cause a loss of control must also be banned, including alcohol for example.
If something is condemned because it mechanically involves something negative, then it automatically creates a category of causes “having that kind of negative consequences”, which must also be condemned.

3. Refutation by Contradictory Consequences

Refutation by contradictory consequences is a type of ad hominem, used in dialectic:

Peter says “S is P”.
The fact that S has the consequence Q: the fact is acknowledged by Peter.
However, P and Q are incompatible.
Therefore Peter is saying incompatible things about S.

Example:

Peter says that power is good.
However, everyone agrees that power corrupts.
Corruption is evil.
Since good and evil are incompatible, power should exclude corruption to be good.
Peter says contradictory things.