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the same error; so that if by certainty we mean absolute freedom from all possibility of error, it is not absolutely certain that twice two are four.
But what is the use of taking certainty in that sense?
Let us adopt a different definition, and call a judgement certain of, and only if, these two things are true of it; first, that the person forming the judgement has no sensible and genuine doubt of its truth, and secondly, that it really is true.
In that sense, I will venture the opinion that a great many things are certain.
However, this hardly concerns the case in hand.

If I am asked how I make sure of the correctness of my logical ideals or norms, I reply that, as will be shown in detail in future lectures of this course I do so by reasoning.
And when I am told that to take sute that this reasoning is correct, I must either assume that all reasoning that seems good is so, or else test it by further reasoning I flatly deny it.
The reasoning is