Uncertainty...................................

Wright thought that metaphysical speculation - ideas about the origin, end, and meaning of life - came naturally to human beings.  He didn't condemn such ideas out of hand, he just thought the should never be confused with science.  For what science teaches is the the phenomenal world -the world we cans see and touch - is characterized, through and through, by change, and that our knowledge of it is characterized, through and through, by uncertainty.
     His favorite illustration was the weather.  Everyone believes that the weather is purely a product of physical cause and effect, but no one can predict it with certainty.  "Unlike planetary perturbations, the weather makes the most reckless excursions from its averages, and obscures them by a most inconsequent and incalculable fickleness," he maintained in one of the first articles he ever published, "The Winds and the Weather," in 1858.  We accept this state of affairs about the weather - that it is a perfectly lawful, rather mundane phenomenon whose complexity nevertheless vastly exceeds our ability to understand it - and yet we freely pontificate about the causes of human unhappiness and the future progress of society, things determined by factors presumably many times more complex than the weather...
      It is not, Wright believed, that every event is not completely determined by physical causes.  It is just that precise knowledge of those causes and how they operate is inaccessible to science in its present state - and considering the multitude of factors, each with its own probability of occurrence, involved in producing the outcome of even the simplest events, such as flipping a coin, that knowledge will probably remain inaccessible.

-Louis Menand,   The Metaphysical Club:  A Story of Ideas in America