and Critical Reasoning
reconstructing an argument
Often, you will have to respond to the arguments put forward by others. In order to do this, you need to be able to figure out precisely what those arguments are! Here are some steps to guide you through this process.
Step 1: Identify the claims that are being made. What conclusion is the text arguing for? What reasons are given for accepting that conclusion? Are there portions of the passage that aren’t part of the argument (because they are asides or digressions, for example)? Are there portions that explain the claims but aren’t themselves additional claims?
Usually the claims in an argument are assertions, rather than questions or commands, since questions and commands cannot be true or false. Sometimes, however, a question implies a clear answer. For example:
Wouldn’t a conscientious driver signal her turns?
might be a rhetorically lively way for an author to advance the claim:
A conscientious driver signals her turns.
Similarly, sometimes a command or exhortation:
Thou shalt not kill.
carries with it a normative claim:
Killing is wrong.
Be aware of these ways of making claims so you can identify them!
Step 2: Distinguish premises (assumptions) from conclusions. The conclusion is the claim the text is aiming to make you believe. The premises are the reasons the text offers to make you believe it.
Although most arguments aim to defend one main claim, sometimes they defend some intermediate conclusions which are supposed to lead us to the main conclusion. Words like thus, so, therefore, and as a result are good verbal clues that the claim which comes next is something the author has concluded from steps that came before. The claim that all of the others lead to is the main conclusion.
Step 3: Work out the logical relation between the claims. Drawing a picture may help here! The argument is supposed to support the conclusion. Try to diagram how the other claims are supposed to hook up to the conclusion. Do some of the claims lead directly to the conclusion, all by themselves? Do others lead to the conclusion only if you take them together with other claims? Do some of the claims lead to the conclusion in a multi-step chain (e.g., assumption A leads to claim B, which leads to claim C, which leads to the conclusion)?
It is possible that the logic in the text is faulty — i.e., that the argument which is presented breaks the rules of one of the patterns of deductive inference. However, this should never be your initial expectation.
Step 4: Fill in implicit premises. Some of these can be inferred by looking at the logical movement in the argument (i.e., a certain conclusion may only be reasonable given a certain background assumption which the author doesn’t make explicit). In other cases, we might infer a relevant background assumption from other contextual information we have (i.e., knowing someone lives in England suggests he makes certain assumptions about the proper side of the road on which to drive).
Step 5: Put the pieces in order. The important order here is the logical order (which might not match the order in which the claims were presented in the text). Number and list the assumption, including any implicit ones, in the best logical order to lead us to the conclusion (which will be the last step).
|course home||course information||handouts||assignments||instructor information||announcements|