TWO KINDS OF PROBABILITY

Chance is the general-purpose word we use when we can see no causal explanation for what we observe. Hitherto I have not needed to quantify our uncertainties but we shall shortly move into territory where everything depends on exactly how large these uncertainties are. I have already spoken of probability in unspecific terms but now I must take the next step. Probability is a numerical measure of uncertainty and numerical probabilities have been used extensively in theological discussions. As we shall see shortly, there are events, such as the appearance of life on this planet, for which the way in which probabilities are calculated is absolutely crucial. Certain events are claimed to have extremely small probabilities and on their validity hang important consequences for what we believe about life on earth or, even, the existence of God. Many of the arguments deployed are often little more than rather wild subjective opinions, so it is vital to be as precise as possible about probability statements.