Maybe it isn’t the clearest way of describing it, but it seems that by “computation of odds” he means using at least some observation of frequencies, and is contrasting this with computing the probability of events for which there have as yet been no occurrences, so no observation of frequency has been possible.
No two real world events are exactly identical. You always need some model to generalize and say the ones you observed are like the ones you predict in some relevant way to reuse the observed frequency in your prediction. Without a model all you can say is that if the circumstances were to repeat exactly, then so would the outcome. And that just isn’t very useful.
Maybe it isn’t the clearest way of describing it, but it seems that by “computation of odds” he means using at least some observation of frequencies, and is contrasting this with computing the probability of events for which there have as yet been no occurrences, so no observation of frequency has been possible.
No two real world events are exactly identical. You always need some model to generalize and say the ones you observed are like the ones you predict in some relevant way to reuse the observed frequency in your prediction. Without a model all you can say is that if the circumstances were to repeat exactly, then so would the outcome. And that just isn’t very useful.