Outline
James Fieser, UT Martin
updated 1/1/2020
This chapter builds upon the basic concepts of argument structure that were presented in chapter 1 (the logic overview). Additional concepts included here are (1) more premise and conclusion indicators, (2) a third type of inference used in argument diagrams, and (3) procedures for analyzing an argument in natural language.
A. PREMISE AND CONCLUSION INDICATORS
1. Inference indicators: words or phrases used to signal the presence of an argument
Two types: conclusion indicators and premise indicators
Inference indicators often have other functions in other contexts; no hard and fast rule
Example:
Since [premise indicator] all humans are mortal, and Socrates is human, it follows that [conclusion indicator] Socrates is mortal
2. Premise Indicators (asterisks indicate new ones not included in the logic overview)
Because
For
For the reason that
Given that
In view of the fact that
Since
*As shown by the fact that
*Assuming that
*Granted that
*Inasmuch as
3. Conclusion Indicators (asterisks indicate new ones not included in the logic overview)
Accordingly
Consequently
For this reason
Hence
So
Therefore
Thus
*As a result
*In conclusion
*It follows that
*The moral is
*This being so
*This proves that
*We can conclude that
*Which means that
*Which proves that
There are three types of argument inferences: (1) joint inference, (2) independent inference, and (3) inference chain. The symbols used for diagraming arguments and their respective inferences are as follows:
Plus sign (+): together with
Arrow (→): intended as evidence for
1. Joint Inference: premises must be taken together to produce the conclusion; each premise independently will not do that
Example Argument: [1] The roof is sagging [2] but it is propped up. [3] Therefore, the roof will not collapse any time soon.
Diagram: 1 + 2 → 3
Example Argument: [1] Everyone at this party is a biochemist, and [2] all biochemists are intelligent. Therefore, since [3] Sally is at this party, [4] Sally is intelligent.
Diagram: 1 + 2 + 3 → 4
2. Independent inference: each premise by itself leads to the same conclusion; distinct arguments for the same conclusion, each of which stands independently of the other
Example Argument: [1] The roof is sagging [2] and it has been leaking for many years. [3] Therefore, the roof will collapse soon.
Diagram: (1 → 3) and (2 → 3)
Example Argument: [1] the grass is way too high, [2] the weeds are out of control, [3] the neighbors think our yard looks shabby, thus [4] it’s time to mow the lawn.
Diagram: (1 → 4) and (2 → 4) and (3 → 4)
3. Inference chain: conclusion of one argument becomes the premise of another
Example Argument: [1] Because I am a human being [2] I am rational; [3] therefore, I am no fool.
Diagram: 1 → 2 → 3
Example Argument: [1] She could not have known that the money was missing from the safe since [2] she had no access to the safe itself. Thus, [3] there was nothing she could have done and so [4] she bears no guilt in the incident.
Diagram: 2 → 1 → 3 → 4
B. ANALYZING THE ORIGINAL ARGUMENT
1. Implicit Statements
Implicit statements: hidden statements in arguments that are incompletely expressed
e.g., the author may intend for the reader to draw the conclusion
Principle of charity: give the arguer the benefit of the doubt, and make the argument as strong as possible while remaining faithful to the arguer's thought
Goal is to minimize misinterpretation
2. Compound sentence: sentence that contains two or more statements
Breakable compounds: it is helpful to break apart some compound statements into two separate ones, such as those that include “and”
Unbreakable compounds: should not be split into separate statements and treated as complete statements (e.g., either-or, if-then, which are not inference indicators)
3. Steps for diagraming arguments
Bracket each statement in a way that best reveals the argument structure
Circle clue words (and, but, therefore)
Number each statement sequentially
Identify conclusion; if conclusion is implied, supply it and number it
Work backwards from conclusion to premises
Determine if any premise leads independently to a conclusion
Determine if there are any intermediate conclusions
Determine which premises need to be taken together