PHL100: Reasoning

Critical Thinking and the Tools of Reason

Critical Thinking
Critical thinking aims to help you decide whether you should believe some claim, or even perhaps just consider it probable, or even just possible. In general, we encounter claims from four kinds of sources:
  1. Reports
  2. Observations
  3. Conclusions of arguments
  4. Products of theories
Philosophers are most concerned with arguments and theories.

1. Reports
Philosophers are least concerned with this. But, reports should be evaluated in terms of the reliability of the source, and any biases it may have.

2. Observations
Observations need to meet either standards of good evidence (such as protection against potential bias) and also may be questioned in terms of the deepest epistemic issues.

3. Arguments
There are three kinds that we need to be concerned with
  1. Deductive. Deductive arguments are measured in terms of whether they are valid. A valid argument is an argument where, if the premises are true, the conclusion must be true.
  2. Inductive. Inductive arguments generalize from some finite number of observations to an indefinite further group of potential observations. Inductive arguments generally are evaluated using standards of scientific reasoning.
  3. Abductive. Sometimes we have a set of explanations before us for a phenomenon, and so we pick the best one. This is abductive reaonsing.
4. Theories
Sometimes we conclude something because it is consistent with or predicted by a theory. There is not complete agreement on how we evaluate theories, but a few criteria are widely considered important. These include, in order of importance: Predictive power is best. However, some theories, such as mathematical theories, do not predict phenomena but rather describe them. We tend to evaluate those theories in terms of how much they explain. (Note that we could drop the first criterion, since rampantly inconsistent theories will have no predictive or explanatory power because they will rule no prediction or explanation out.)

Other Philosophical Tools
Along with primarily evaluate arguments and theories, philosophers are also often engaged in conceptual clarification. This is often very important, and leads to breakthroughs. (Similar kinds of clarification occur in mathematics, it is worth noting.)