Choose carefully, words mean things.

Faith must trample under foot all reason, sense, and understanding.
Martin Luther

   In the English language there are many ways to express similar thoughts.  Most never bother to learn if what they are saying is correct.  They say "decimate" which means reduce by ten percent, when they mean "destroy"; probably because they think using a bigger word makes them sound smarter.  "Stupid" and "ignorant" are used interchangeably, despite having nearly opposite meanings.  I can't tell you how many times I passively forgive someone saying "mute" when they meet "moot".  This post is not about that.  rather I will be focusing on the lesser known evils: "know", "believe", and "feel".
       When someone says they "believe" something; such as, "I believe free healthcare is a right." they are really saying that no matter how sensible your argument against the idea, they will not change their opinion.  Belief, by definition, is an idea held despite the lack of evidence.  Belief is usually backed up by tradition, and is a type of self-enforced ignorance.  People who use this type of phrase are saying that it is pointless to argue with them.  Yet this wording seems soft compared to "Knowing" something.
       When someone uses the word "feel" they are also saying that they will not listen to evidence.  Phrases such as: "I feel that people are better left to their own devices for healthcare." indicate this level of obstinacy.  The difference between someone who "believes" something, and someone who "feels" something is the weight of accord.  Belief implies a group of people with the same idea; or at least the same foundation that led to the idea.  This is a type of self-enforced ignorance as well.  This wording too, despite its clearly argumentative connotation, seems softer than to "know".
       When someone says they "Know" something it implies they have a measure of understanding of the topic; and more-so, the capacity to change that knowledge.  The statement "I know the Bill of Rights does not address healthcare." is a statement of learned perspective.  This also has the advantage of being malleable.  In light of new evidence knowledge, by definition, changes.  Thus the wording which sounds firmest, "I know this", is really the softest.  Any ignorance in this case, can be corrected without incident.
       So be careful when debating.
       I believe this should make you feel inclined to use the word "know" more often.