Direct measurement of temperature

by Neil Rickert

In an earlier post, I described the representation measurement of temperature.  In this post, I describe the direct method.  The contrast is intended to illustrate the distinction between representational theories of perception and direct theories of perception.  By using an example from science (or perception written big), we illustrate in a way that is easier to see.

The design of the instrument

The design is almost the same as described in the earlier post.  There is one addition.  The mercury column in the capillary tube is directly calibrated in temperature.  That is to say, there are graduation markings on the thermometer, from which we can directly read off the temperature.

How it works

It works in much the same way as the representational system, but without the computation.  We directly read off the temperature from the calibration scale on the capillary tube.  So no computation is required.  The physics is the same, but the computation can be skipped.

Knowledge and truth requirements

In the earlier post, I listed several knowledge and truth requirements.  None of those are requirements for direct measurement.  We required those in the representational measurement, because they provided the algorithm to be used in the computation, and the parameters for that algorithm.

Because there is no computation, there is no required knowledge to be used in a computational algorithm.  So all of those requirements disappear.

In place of those earlier requirements, we do need that the thermometer be correctly calibrated.  But even that might not be needed.  For the first thermometer ever made, we can use a completely ad hoc calibration scheme.  And then we can make that our standard, and require other thermometers to be consistent with that ad hoc standard.

In other words, the requirements become that of consistency of the calibration over the various instruments that we might use for measuring temperature.  This is more of a pragmatic requirement than a truth requirement.

Plantinga’s EAAN

For the representational case, we saw that Plantinga’s EAAN (evolutionary argument against naturalism) amount to an argument that evolution could not meed the truth requirements.  For direct measurement, as we have seen, there are not truth requirements.  The only requirement is the pragmatic one of calibration consistency over the various measuring instruments.  Evolution is a pragmatic system.  So Plantinga’s argument has no sting.

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