Writing can have several goals. Two of particular interest are the goal to inform, and the goal to persuade. These two goals are not inherently incompatible, but care should be taken in trying to combine them.
To inform is to convey facts. The model here is reporting. One of the goals is objectivity. Now, complete objectivity is not obtainable. Biases are inevitable. One of the first biases is in which stories are reported, both individually, and over time. For instance, if I choose to write a series of articles on a particular corrupt politician, I am, by not reporting on other politicians, scandals, etc., subtly implying that this case is somehow unique, or worse than others. This may or may not be true, and the bias may or may not be intended. I cannot very well write hundreds of articles, so I have focused on one topic. The hope is that my writing, combined with those of others with diverse views and areas of expertise, will help dilute the bias over time. If I write for a magazine whose editors chose not to include diverse views along with mine, an overall bias appears in the publication. This is hopefully diluted out by the myriad of other publications available. So the way to counter bias inherent to the choice of subjects is to create volume. More sources of information equals greater diversity of views. See the example of totalitarian societies that limit both sources of information, and access to them.
Persuasion is simpler in that, in its purest form, its biases are intentional, visible, and clearly stated. The model here is the editorial. The editors state a viewpoint and make an argument designed to convince the reader.
Neither of the above contain intentionally hidden biases. In the first case, bias is avoided, but can “creep” in unintentionally. In the second case, bias is clearly stated. In either case, ‘’deception’’ can skew the purest example of each form. Deception is the intention, but unstated, insertion of bias. For instance, if I am reporting on a corrupt politician, and I report on a bribe taken, citing false or weak sources to strengthen my story, I have inserted an occult bias when the reader expects objectivity; hence, deception.
If I am writing an editorial, deception is more subtle, because it is assumed that I will be biased, and that I am trying to convince others of my position. If I use tactics other than simple persuasion, I am being deceptive. For instance, if I am trying to convince my reader that political corruption is the greatest danger to our democracy, and I create an impression that it is more widespread than it actually is, I have deceived.
So, as a consumer of writing, public speaking , or other mass communication, it is important to know whether someone is trying to report or persuade. Next, one must decide if deception is being used. The greatest protection against bias and deception is to consume information from many, and diverse sources. If you are a Democrat, it is foolish not to listen to Republican speakers. If you are a cardiologist, you must not just read literature from drug companies, but also read original research from as many sources as possible. Intelligence requires eternal literacy.