  Against powerful currents of determinism that derived from the Enlightenment philosophy of the eighteenth century, Peirce urged that there was not the slightest scientific evidence for determinism and that in fact there was considerable scientific evidence against it. Always by the words “science” and “scientific” Peirce understood reference to actual practice by scientists in the laboratory and the field, and not reference to entries in scientific textbooks. In attacking determinism, therefore, Peirce appealed to the evidence of the actual phenomena in laboratories and fields. Here, what is obtained as the actual observations (e.g. measurements) does not fit neatly into some one point or simple function. If we take, for example, a thousand measurements of some physical quantity, even a simple one such as length or thickness, no matter how carefully we may do so, we will not obtain the same result a thousand times. Rather, what we get is a distribution (often, but not always and certainly not necessarily, something akin to a normal or Gaussian distribution) of hundreds of different results. Again, if we measure the value of some variable that we assume to depend on some given parameter, and if we let the parameter vary while we take successive measurements, the result in general will not be a smooth function (for example, a straight line or an ellipse); rather, it will typically be a “jagged” result, to which we can at best fit a smooth function by using some clever method (for example, fitting a regression line by the method of least-squares). Naively, we might imagine that the variation and relative inexactness of our measurements will become less pronounced and obtrusive the more refined and microscopic are our measurement tools and procedures. Peirce, the practicing scientist, knew better. What actually happens, if anything, is that our variations get relatively greater the finer is our instrumentation and the more delicate our procedures.  (Obviously, Peirce would not have been the least surprised by the results obtained from measurements at the quantum level.)