“It is difficult to get a man to understand something, when his salary depends upon his not understanding it!”

-Upton Sinclair

When selecting information sources in your pursuit of critical thinking it is vitally important to take into account any conflict of interest (COI) of your sources. Someone making an argument that has a vested interest in the side they are advocating is much more likely to be biased whether the bias is conscious or not.

For example, suppose a woman dies suspiciously while in police custody. The police conduct their own investigation and find the officers involved did nothing wrong. Clearly the police are biased, as law enforcement officers they don't want to be seen breaking laws themselves. Because of this there may be unconscious or even deliberate efforts to put themselves in a good light.