Philosophers and participants on this boards love to talk about arguments and a few of them love to talk about soundness of arguments [like here What are some criticisms of Epicurus' "death is nothing to us"? ]

Coming from a study of formal language, the striking feat of their initiative is their desire to stick to a notion of soundness and acceptability of an argument, becomingly without even saying in what logic they work, without even saying what is soundness, beyond some implicit notion of personal vague acceptability [coming down to ''I like this statement so I objectify it and I call it sound'', ''I do not like this statement, so I objectify it and call it unsound''] expressed, in their syntax and vocabulary, as some fantasized objectivity [in order to attempt to persuade other parties to change side ?] ...

So what is soundness for a natural language ?

  • This is less of a question than an attempt at an insult. The writer has already decided that what we do is decide what we like and declare it sound. What is the point of answering the question?
    – user9166
    Jun 13, 2017 at 21:24

1 Answer 1


Soundness is a logical concept, and when a philosopher uses the word, she means the logical concept. Soundness is not a property of a statement, but that of an argument. An argument is defined as a set of statements where one statement is a conclusion and all the others are viewed as premises (or assumptions). An argument is staged to show that the conclusion of the argument has to be true. For this, an argument must be both valid and sound. By definition, an argument is valid when it is logically impossible for all its premises to be true and its conclusion to be false, In other words, if all its premises are true, in a valid argument, the conclusion must be true. Also by definition, an argument is sound when it is valid and all its premises are true. Ergo, the conclusion of a sound argument is always true. For this reason, soundness is the ultimate virtue of an argument. (By the way, the above material is taught in any intro to logic course).

Philosophers draw different, sometimes, conflicting, conclusions, because they disagree on the truth of some of the premises. For example, pro-choice theorists tend to assume that a fetus is not a person, and more like a tumor. To establish this assumption, they might appeal to the fact that both tumor and fetus share similar aspects (unwanted, growing big, hindering the ability of moving around freely). Once establishing the identity (fetus = tumor), they can conclude that it is morally permissible to remove a fetus from one's body. Pro-life theorists, by contrast, assume that a fetus is a person. To prove this assumption, they will try to appeal to the fact that human society and culture have treated a fetus like a baby. Once establishing the identity (fetus = baby), they can conclude that it is morally impermissible to kill a fetus since it is morally impermissible to kill a baby.

As issues surrounding abortion arguments show, all the heavy lifting is done through establishing the truth of the premises (no philosopher proper would make a mistake in the validity of an argument), which is nothing but showing the soundness of the argument.

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