- Combinatorial and frequentistic ``definitions'' give useful rules for evaluating probability, although they do not, as it is often claimed, define the concept.
- In the axiomatic approach one refrains from defining what the probability is and how to evaluate it: probability is just any real number which satisfies the axioms. It is easy to demonstrate that the probabilities evaluated using the combinatorial and the frequentistic prescriptions do in fact satisfy the axioms.
- The subjective approach to probability, together with the
coherence requirement,
__defines__what probability is and provides the rules which its evaluation must obey; these rules turn out to be the same as the axioms.

Since everybody is familiar with the axioms and with the analogy
(see Table
and Fig. )
let us remind ourselves of the *rules of probability* in this form:

**Axiom 1**- ;
**Axiom 2**- (a certain event has probability 1);
**Axiom 3**- , if

**1:**- ;
**2:**- ;
**3:**- if then ;
**4:**- .

**5:**