Critical thinking a concise guide by Tracy Bowell & Gary Kemp, fourth edition – Summary chapter 5

A lot of things people write plays no argumentative role. It can serve the function of emphasis, rhetoric or something else. This extraneous material should not be included in the reconstructing of an argument. The word ‘since’ transforms a conditional statement into a statement that asserts both the conditional and the antecedent of that conditional. The first step in reconstructing an argument is to make a list of the argument’s premises and conclusion that leaves out extraneous material.

DEFUSING THE RHETORIC
Metaphors, slang and expressive epithets should be eliminated while reconstructing an argument. Expressive epithets are terms used to refer to some person, group or other entity, without actually using the name.

LOGICAL STREAMLINING
When reconstructing arguments, the logical relationships should be displayed in the simplest, clearest and most familiar ways possible. There are two rules of thumb when logical streamlining:

1.        Where appropriate, rewrite sentences as either conditional or disjunctive sentences in simple forms.
2.       Rewrite generalisations in simple forms using a clear quantifier.

IMPLICIT AND EXPLICIT
In arguments, some essential propositions are left implicit. Reconstruction of arguments should make all propositions explicit. The first step is always identifying the conclusion. The next step is identifying the argument’s premises. The third step is making any implicit statements explicit.

CONNECTING PREMISES
A connecting premise is a premise that has to be made explicit in order to make the argument valid. The connection premise can be not true or not lead to the argument being valid.

COVERING GENERALISATIONS
Asserting conditionals often happens on the basis of some covering generalisation. The conditional often relies on a generalization.

RELEVANCE
Whether a certain premise is true or false is not always equally relevant.

AMBIGUITY AND VAGUENESS
In reconstructing arguments, ambiguity and vagueness have to be eliminated. If we are unable to choose one interpretation of an ambiguous term when reconstructing an argument, they should all be presented. While reconstructing an argument, vagueness should be eliminated where possible as this clarifies the argument and allows us to focus on the matter, without being distracted by a vague and possibly controversial term.

PRACTICAL REASONING
Practical reasoning or means-end reasoning refers to reasoning that includes a practical conclusion. It includes desirable or undesirable outcomes. For practical reasoning, the cost and the benefit of the outcome must be considered.

BALANCING COSTS, BENEFITS AND PROBABILITIES
If an argument is represented as inductive, the cost, benefit and probability have to be discussed and weighted. The expected value can be used to systematically give an overview of the costs, benefits and probabilities of things happening. To calculate the expected value, the cost or benefit of the action is multiplied with its probability. The expected value should be maximised.

EXPLANATIONS AS CONCLUSIONS
Abduction is also called inference to the best explanation. There is a distinct pattern when explanations are used as conclusion:

P1) Agreed fact
P2) Agreed fact was caused by either A, B or C
P3) B is not the case, neither is C
C) Agreed fact was caused by A

CAUSAL GENERALISATION
Causal generalisations (e.g. smoking causes cancer)  not tell us to what degree the one thing raises the probability of the other thing.