Kidd.— On Probability. xlix 



G. (Probability implies imperfect knowledge and rationality.) — The percep- 

 tion of probability, therefore, pertains to minds that have only a partial 

 knowledge of the thing in question, and are rational These two conditions 

 must be combined in order to the perception of probability. To a being 

 omniscient of the relations pertaining to any object of thought, there is, with 

 respect to that object, a full certainty of direct knowledge, so that there is no 

 place for probability. Such, for example, is the case of our own knowledge 

 with reference to abstract relations of number and magnitude. On the other 

 hand, a being totally irrational is incapable of the mental pondering that a 

 perception of probability implies. In a mind devoid of reflection there is no 

 distinction between vivid impression and belief. The perception of probability 

 implies a combination of imperfect knowledge with rationality. 



7. ( Probability is a property of Propositions. J— We have seen that Pro- 

 bability is not an attribute of the events themselves respecting which we may 

 inquire. It would be idly pedantic to condemn, or on all occasions to refrain 

 from, the usual phraseology, whereby we speak of probable events, facts, etc. ; 

 but it is to be noted that these expressions are authorized only by custom and 

 convenience. Of what, then, is Probability a property? When we say that 

 something is probable, what is it that we thus assert to be worthy of our 

 acceptance, or to have some degree of acceptibility ? 



To ascribe probability to a supposed event is to allege, that the supposition 

 of the event's occurrence is a probable supposition ; that it is, in other words, 

 a supposition having a certain amount of claim to be accepted as in accordance 

 with fact. A supposition is itself a fact, a mental phenomenon ; but its value 

 usually consists in its relation to another, an objective, fact, whether this be 

 mental or otherwise. Imaginations may be vain, thoughts may be erroneous ' 

 and they are so in proportion as they are inconsistent with objective reality. 

 To designate a probability is to estimate the claim of a supposition or 

 hypothesis as to its being in accordance with fact. To say that the event A 

 is highly probable, is to indicate that the supposition of the occurrence of A is 

 to be provisionally received as having an evidence approaching to certainty : 

 to assert that the event B is morally certain, is to declare that the evidence in 

 favor of that conclusion is practically equivalent to opportunitv of absolute 

 knowledge. Probability, then, is an attribute of suppositions as compared 

 with the known data of objective reality. Now, all suppositions are, or are 

 expressible in, propositions — i.e., declarations or statements; and they are 

 unsusceptible of full consideration except as so expressed. We may, therefore 

 assume the following principle, that Probability, like Truth, is a quality of 

 propositions, and of propositions only. By saying that a supposed event is 

 probable, in whatsoever degree, we mean that this degree of probability 

 pertains to the supposition of the event, or to the proposition in which that 

 hypothesis or judgment is stated. 



