Humans occupy a special place in creation.  We are blessed with a self-awareness that is perhaps unique in the universe.  And it is this spark of consciousness that drives the creation of art and mathematics and science and contemplations of origins and purpose.  Or as Carl Sagan quipped, “Man is the means by which the universe comes to know itself.”


But despite our scholarship and technological prowess, we have as yet been unable to achieve any absolute certainty.  Indeed we now have well respected demonstrations that most, if not all, features of reality are indeterminate.   And significantly these constraints on our hubris apply to both religion and science which rather than being distinct share common assumptions, methods, and certitudes.


But while rational doubt is an inescapable feature of the human condition, we are not defenseless against unavoidable limits on certainty.  Nor are we at the mercy of mystical and capricious forces beyond understanding.  Rather we are blessed with rationality, the evidence of observation and experience, and the thoughts and recorded wisdom of others.  And our ability to refine and enlighten what understandings we can achieve remains the marvel of creation.




The sources of knowledge are several and well known.  They fall into mostly self-evident categories as follows.


1.      Self Awareness.  We have thoughts and thereby know we exist.  This was succinctly expressed by Rene Descartes as “cogito ergo sum [I think therefore I am]”.  We can remember the past.  We can extrapolate from experience and imagine future events.   We can dream of what never happened and even of what could never happen.


2.      Perception.  Most obviously we have the direct evidence of our senses.  We can see the world.  We can feel the warmth of the sun and the cold of the night.  We can touch a surface and know whether it is rough or smooth.   Our senses allow us to take the measure of the greater world around us.


3.      Reason.  We can form abstract ideas and judge their relative merits.   Our logic forms the basis of geometry and indeed of all mathematical pursuits.  Our minds can imagine perfect forms unattainable in the natural world.  And this is knowledge that is just as real as sensory input but which could never be discovered or demonstrated by physical measurement.  A famous example from antiquity is the fact that the square root of two, which is the diagonal length of a unit square, cannot be expressed a fraction containing only whole numbers.  And modern mathematics provides any number of similar examples.


4.      Shared Morals.  Every human being has a conscience which acts to restrain selfish needs and wants.  Even as children we know the difference between right and wrong.   And while we share instincts with even the lowest forms, our inner sense of right and wrong sometimes compels acts contrary to even our very survival.  Societies universally eulogize selfless heroes who give their lives to save even unrelated individuals.


5.      Communicated Experience.   Others can tell us of what they have experienced.  And beyond that we can know their hopes and fears and thoughts and discoveries.  With the advent of the written record, we can access the collected wisdom of even those who have long since passed.   And this store of information across countless generations is many times larger than all others combined.


6.      Sacred Scripture.   This refers to revealed truth from a supernatural source and is thus controversial.  But if we believe in the existence of free will not strictly determined by natural law, then our every conscious choice has a touch of the supernatural or that which is above or beyond nature.  Also given the evidence for a “Big Bang” origin of the universe, this source cannot be considered unreasonable since it is logically impossible for the universe to have created itself from nothing under the sole agency of natural law.  Nor is a Creator inconsistent with observations of increasing entropy, meaning the state of disorder, which also implies a physical beginning “ex nihilo”.




While other means to knowledge are sometimes proposed, they are in general terms but different sides of the same coin.  That is they are but alternate descriptions of those already given above.  Some of these include the following.


1.      We have a homeostasis or our self regulating body chemistry as well as our involuntary autonomic reflexes whose results we can sense but in the same qualitative manner as external stimuli.


2.      We have an almost instinctive kinesthetic awareness of our surroundings and our position in it.  This provides a muscle memory allowing us to walk and run, to hit a baseball, and to play the piano with more ease than might otherwise be the case.


3.      We have an instinctive fear of falling or of snakes or of lightening but again this is triggered by a sense of our surroundings and our imaging the danger.


4.      If we are passionate about observing people and well enough practiced, we may almost subconsciously form snap judgments of another’s thoughts or intent.  Because humans are similar enough to share common instincts and concerns, we may recognize our own situation in others from the most subtle clues and infer another’s thoughts almost as if we could read minds.


5.      We tend to learn from our own mistakes albeit in a often haphazard and inconsistent fashion.


6.      In a similar fashion we may make an almost involuntary connection between various ideas and experience a flash of insight.


In every case these latter items are derived and not fundamental sources different from those previously described.  In addition the information they convey to our conscious mind are of a constructed and secondary quality




Many of these considerations have been collected under the topic of Epistomology which is the study of truth or “justified belief”.  Unfortunately while we must believe that truth exists, absolute certainty is a logical impossibility to include both faith and science.  Also knowledge is not understanding much less certainty.