An argument is a set of sentences, one of which the others are offered in support of. Rewrite a passage as numbered premises and a single conclusion, strike the sentences that do no work, and see in a table of cases what it would take for the support to fail.
Core ideas
Philosophy is mostly argument, and an argument cannot be tested until it has been taken apart. Standard form is the taking apart.
No sentence is a premise or a conclusion in itself. The same sentence is a conclusion in one passage and a premise in the next. The role is fixed by what the author is trying to get you to accept, and by what is offered for it.
The conclusion may come first, last or in the middle. Words such as “therefore” and “hence” flag a conclusion; “since” and “because” flag a premise. They are clues to the author's intention, not a rule.
To ask whether the support could fail, we need the ways the world might be, so far as the sentences are concerned. With two simple sentences there are four: both true, only the first, only the second, neither. Each is a row of a table.
The material
Standard form is a layout, not a theory: premises numbered, a line, one conclusion. What matters is what the layout makes visible.
An argument is a set of sentences in which one, the conclusion, is offered as supported by the others, the premises. A passage that states claims and offers no support for any of them is a description, not an argument.
Everyday passages do not come in that layout. They begin with the conclusion, trail off into asides, repeat themselves and leave out the step that everyone is assumed to grant. Writing the passage in standard form means deciding, sentence by sentence, which job it is doing.
“The streets are wet. Streets here are only wet after rain. So it rained.” The last sentence is flagged by “so”. Set out, it reads: P1, the streets are wet; P2, streets here are wet only after rain; C, it rained.
Three kinds of sentence turn up in a passage, and only the first two belong in the standard form. Premises give the support. The conclusion is what the support is for. Everything else — a digression, a repetition, a flourish — does no work, and the test is whether deleting the sentence changes what the passage gives you reason to accept.
The conclusion is the sentence the others are offered in support of. Find it by asking what the passage wants you to believe or do, not by looking at the end. “The bus will be late, since the road is closed” puts the conclusion first and the premise last.
A table of cases makes the idea of support exact. Let p stand for “the streets are wet” and q for “it rained”. With two sentences there are two possibilities each, so four cases.
The lab below takes premises and a conclusion and lists these cases. It marks any case in which every premise is true and the conclusion false, because that is the case in which the support has failed. Later in this course the same table decides validity; here it is used only to show why one premise p does not support a different sentence q, and why adding a premise that is not used changes nothing.
One limit, stated once. The lab works with simple sentences named by single letters. Whether “it rained” is the right way to put the author's claim is a judgement you make while writing the standard form, and no lab checks it.
Interactive
Every row, every counterexample, and the form
Method
Four moves, in this order. The third is the one people skip.
Ask what the passage wants you to accept. That sentence is the conclusion, wherever it stands. If you cannot find one, the passage may be a description, and there is nothing to set out.
“Therefore”, “so” and “hence” point to a conclusion; “since” and “because” point to a premise. Treat each as a clue and check it against the first move.
Delete a sentence in your head. If the support for the conclusion is unchanged, it was padding: an aside, a repetition, a rhetorical flourish. Leave it out of the standard form.
Number the premises, draw a line, write the conclusion once. Put each claim as a complete sentence, and add a missing premise only when the passage plainly depends on it, saying so.
The passage: “The streets are wet. Streets here are only wet after rain. So it rained.” Let p be “the streets are wet” and q be “it rained”.
The lab cannot take P2 yet, because P2 is a conditional and the connectives come in the next lessons. What it can take is P1 alone. In the leap preset, p is the only premise and q the conclusion, and the lab finds one row where the support fails: p true and q false, the streets wet and no rain. P2 is exactly the sentence that rules that row out, which is why the passage needed it, and why an author who leaves it unstated is still relying on it.
Given a short passage, write numbered premises and one conclusion, name the sentences you left out and say why each does no work, and say which sentence the others are offered in support of. A layout without those reasons is a guess.
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