Here, coercion is taken to be the method of persuasion which encompasses all logical fallacies; lying, lying by omission, or embellishment; emotional and otherwise logically unsound arguments; and physical threats. Deceived is taken to mean led to believe something which is untrue. If someone is convinced of something which is in fact already true, but they believe it is true for the wrong reasons, have they been deceived? Have other philosophers discussed this question?
The traditional definition of knowledge is called justified true belief. A person P has knowledge of a fact 'A' if the following three conditions are satisfied:
- A is true
- P believes A
- P's reasons for believing A are justified/rational.
In the scenario you mention, the person is not justified in his/her belief, so the situation you are describing would count indeed as deception. Consider the following real world scenario: A sick person is sold a medicine that will cure him from his aliment. The medicine is indeed effective, but the person who sold him the medicine said that the medicine works using the Jedi Force. Clearly the sick patient is not justified in believing that he was cured by the Force, and the person who sold him the medicine unambiguously deceived him, by causing him to hold this false belief.
A closely related issue you might want to examine, is Gettier's problem, which shows that in some cases, a belief can be justified and true, but still not count as knowledge.