Critical thinking takes place in a mental environment consisting of our experiences, thoughts, and feelings. Some elements in this inner environment can sabotage our efforts to think critically or at least make critical thinking more difficult. Fortunately, we can exert some control over these elements. With practice, we can detect errors in our thinking, restrain attitudes and feelings that can disrupt our reasoning, and achieve enough objectivity to make critical thinking possible.

The most common of these hindrances to critical thinking fall into two main categories:

(1) Those obstacles that crop up because of how we think and
(2) those that occur because of what we think. The first category is comprised of psychological factors such as our fears, attitudes, motivations, and desires. The second category is made up of certain philosophical beliefs.

None of us is immune to the psychological obstacles. Among them are the products of egocentric thinking. We may accept a claim solely because it advances our interests or just because it helps us save face. To overcome these pressures, we must

(1) be aware of strong emotions that can warp our thinking,
(2) be alert to ways that critical thinking can be undermined, and
(3) ensure that we take into account all relevant factors when we evaluate a claim.

The first category of hindrances also includes those that arise because of group pressure. These obstacles include conformist pressures from groups that we belong to and ethnocentric urges to think that our group is superior to others. The best defense against group pressure is to proportion our beliefs according to the strength of reasons.

We may also have certain core beliefs that can undermine critical thinking (the second category of hindrances). Subjective relativism is the view that truth depends solely on what someone believes -- a notion that may make critical thinking look superfluous. But subjective relativism leads to some strange consequences. For example, if the doctrine were true, each of us would be infallible. Also, subjective relativism has a logical problem -- it's self-defeating. Its truth implies its falsity. There are no good reasons to accept this form of relativism.

Social relativism is the view that truth is relative to societies -- a claim that would also seem to make critical thinking unnecessary. But this notion is undermined by the same kinds of problems that plague subjective relativism.

Philosophical skepticism is the doctrine that we know much less than we think we do. One form of philosophical skepticism says that we cannot know anything unless the belief is beyond all possible doubt. But this is not a plausible criterion for knowledge. To be knowledge, claims need not be beyond all possible doubt, but beyond all reasonable doubt.