The word force is used with three distinct meanings:
The graduated concept of force of an argument exists in opposition to the binary notion of valid or invalid argumentation. An argument is strong (or weak) either in itself or relative to another argument. This force is evaluated according to different criteria.
1. Inherent strength of an argument scheme
In scientific fields, to be strong an argument must first of all be valid. That is to say that it must develop according to a method which is accepted in the given scientific field. Yet, an argument can be valid and not so strong, that is to say, really relevant and interesting for the discussion of such and such hypothesis.
From a philosophical point of view, one might consider that some argument schemes are by nature stronger than others. The strength of an argument is thus determined on the basis of ontology. An adept of moral realism will consider that an argument based on the nature of things and their definition is stronger than a pragmatic argument; a practical mind will think the opposite.
2. Strength and effectiveness
In relation to a goal such as persuasion, the strongest argument will be the most efficient, the argument that most quickly achieves the arguer’s goal, whether it be selling a product or electing a president. A degree of strength can be attributed to the argument on the basis of an impact study carried out on the relevant target population, S. Persuasion.
3. Strength of an argument and acceptability by an audience
The New Rhetoric defines the strength of the argument according to the extent and quality of the audiences that accept it, S. Persuade, Convince.
4. Strength and linguistic reinforcement of arguments
Two arguments oriented towards the same conclusion belong to the same argumentative class, S. Orientation. Both bring some support to this conclusion. Within the same argumentative class, the strength of an argument can be determined by reference to an objective gradation, such as the scale of temperature, or it may simply be allocated to the argument by the speaker, who value such argument over another. The hierarchization is marked by the means of argumentative morphemes (for example, even) and realizing or de-realizing modifiers. The arrangements of the arguments on argument scales are governed by the laws of discourse.