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.  

It is what it is.

       OK.  See that bit of idiocy up there.  The title.  Worst bit of tautology ever conceived by the English speaking world.  Lets begin our forensic disassembly of this moronic bit of language.  First, if course "it is what it is".  What the hell else could it possibly be.  It goes without saying that this expression goes,... without saying.  It not only is a statement of the painfully obvious, it is also...

       Untrue.  The primary argument people raise against M-theory (its string theory, science stuff, you don't actually need to know anything about it, just play along.)  Anyway, the primary argument against it is that it cannot be proven false.  Therefore, reflexively, it cannot be proven true.  Much like the canned idiocy that is, "it is what it is".  Aside from being obvious and untrue it is also...

       Passive aggressive.  There are ways to express that further action will not help that do not place the blame nowhere in particular.  One might say, "Oh, well, what can you do?"  That phrase places the onus for action on the person hearing it.  Also there is "Que sera, sera."  or in English, "What will be, will be."  This at least places the inevitable in the future where it may or may not be acted on.  But moreover these phrases are used in particular ways, to achieve effect.  "It is what it is" is a phrase used in a host of inappropriate ways.  "Why aren't I getting a raise this year?"  "Well there's no money left in the budget so, it is what it is."  It adds nothing to the conversation except a second.  That is a second you will not get back.  

       A coworker once used that banal idiocy in a conversation with me and I told him, "Stop.  Don't use that moronic phrase, man.  You're better than that."  He agreed.  (Although I did catch him saying it again)  Certain phrases, like this one should be avoided at all costs, because it tells the world they are dealing with an idiot...

       Who is not worth talking to.  There's the silver lining.  I no longer need to wonder if the person I'm talking to is the sort of person who when being asked about the average level of intelligence replies, with no sense of irony, "I think most people are smarter than that."  (actual conversation.)  "Than average"  I said.   "Yes"

"You are saying that most people are smarter than average?"  I condensed.  "Yes"  They replied.  

       But if they had replied with "it is what it is" I would have known them for an idiot without the need for clarification.  (Most people may be smarter than the average level, if there are more profoundly retarded people than geniuses.  But such things are beyond the grasp of the person I was talking to, and not within the scope of the conversation.  Just for clarity's sake).  By the way, I have sworn off ever uttering such ridiculous drivel as that cursed phrase.  The only time I have employed it is here, and it will be the last.