A Primer to Logic: The Role of Sentences in an Argument

In previous posts, I’ve discussed the role of words along with problematic language within arguments. In this post, I elaborate on another basic unit of an argument – sentences.

An argument is made up of sentences that either make a claim (that which asserts something) or provide reasons (support for the assertion). For an argument to be effective, however, just any kind of sentence will not do. Recall from your grade school English class the various kinds of sentences you encounter in the English language. You encounter interrogative, exclamation, or imperative, declarative statements. For an argument to exist, there must be a sentence that asserts something either is or is not.

An interrogative sentence (a question) cannot assert anything, nor can it either offer support for an assertion (for a possible exception, see Chapter 3). Thus, for example, a series of rhetorical questions cannot serve as an argument. An explanation cannot assert anything as well. Generally, an exclamation expresses an emotion or state of being of the subject. If an assertion is inherent in an exclamation, then it ought to be explicitly stated so that the audience is clear about what is being asserted. Finally, an imperative (or a command) cannot make an assertion nor provide support for a claim. A command is used to communicate an expectation of person A for person B. Person A does not intend to argue the truthfulness of their command; rather, they expect obedience or suffer the consequences.

A declarative statement is a sentence where the communicator seeks to relay some kind of information. We are closer to discovering what kind of sentence make up effective arguments, but in order for this discovery to happen, we must first whittle away those kind of declarative sentences that do not make an assertion. For a declarative statement to make an assertion, it must be either true or false.

A piece of advice, such as “Be sure to avoid Bob’s Taco Tent if you have indigestion,” does not assert anything; rather, it is someone’s suggestion for another person to consider. It is neither true nor false that Bob’s Taco Tent exacerbates one’s indigestion; it could be that someone with indigestion finds that Bob’s food does nothing to worsen their indigestion. Similar to a piece of advice is one’s opinion. For instance, one may believe that grilling with charcoal makes food taste better than grilling with a gas grill. While one is indeed making a claim, merely stating an opinion does not an argument make. Instead, they state something that can (and does) vary depending on the person and (at times) the quality of one’s grilling skills.

In order to distinguish between declarative statements that do make an assertion and those that do not, some logicians prefer to use the word proposition for statements that do make an assertion. This helps to set apart statements that make assertions from those that do not. It should be noted that the use of proposition is not universal among logicians; some prefer to use sentence while others use statement. It is the opinion of these authors, however, that the use of proposition helps to avoid any confusion with other types of sentences.

Propositions, then, serve as the bones of an argument. In Chapter 2 we will look at the specific parts of an argument and what role they play. For propositions to make up an argument, one proposition must be affirmed by other propositions. That is, the propositions must make an inference. A passage (or a group of sentences) can be made up of propositions but not make an argument. Passages of this kind are called non-inferential passages. This will be discussed in greater detail later in Chapter 2. Right now, we will turn to the discussion of the role of context and setting in an argument.

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