invoked as a means of catering for this uncertainty. To explain uncertainty,
however, it is first necessary to consider the basis of certainty.
Certainty
Where a person is certain that they know something they believe that it is true
with a probability of 100%. They are certain about the truth when either of two
things happen. They have observed something, such as X or Y, for
themselves.
Or, they have observed one thing (about which they are then certain), and they
are also certain about a behavioural law which takes either of two forms:
(1)
Another thing will happen in consequence of the first. This can be
written in the form: “When X occurs Y will (later) occur”.
(2)
Another thing has happened to cause the first. This can be written in the
form: “When Y has occurred X has occurred beforehand because X is the
sole cause of Y”.
Uncertainty
In other cases a person is not certain about the truth. Why are they not certain?
They are not certain for either or both of two reasons:
(1)
They are not certain about X or Y because they have not observed
either of these for themselves, or they have observed but have not observed
them properly.
(2)
They are not certain about the truth of a behavioural law which enables
them to say either of two things. (a) When X occurs Y will (later) occur. (b)
When Y has occurred X has occurred beforehand because X is the sole cause
of Y.
In these cases when they are not certain about X or Y they believe that X or Y
is true with a probability of something less than 100%, that is, something
falling between 0% and 100%.
This analysis reveals the fundamental point. We cannot predict the future or
know the past with certainty when we do not have perfect information. In the
absence of perfect information it is necessary to resort to probability. If we
cannot know something for certain the next best thing is to know, as a
plausible estimate, the chance of it occurring. For example X is a disease and
we believe, following research, that it will occur in about 37% of the
population.
Using probability is reassuring because it reduces uncertainty. Reducing
uncertainty is an advantage for at least two reasons. First, uncertainty makes
most of us anxious. Second, individuals, institutions and society can make
plans for the future. For example, if a disease will occur in 37% of the
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