650. This surely means: the possibility of a mistake can be eliminated in certain (numerous) cases. – And one
does eliminate mistakes in calculation in this way. For when a calculation has
been checked over and over again one cannot say “Its rightness is still only very probable – for an error may always
still have slipped in”. For suppose it did seem for once as if an error had
been discovered – why shouldn’t we suspect an error here?
the mistake doesn’t exist –
what you deal with in any calculation – is uncertainty
when you check a calculation –
you are recognising uncertainty
the rightness of the calculation –
is an assumption –
effectively a pragmatic assumption –
you assume the rightness –
to go forward –
this assumption – like any assumption –
is open to question –
open to doubt
this does not stop us operating –
uncertainty –
it is the ground of action
‘for an error may always have slipped in’ –
is only to say –
you can nev er be sure
you follow practises –
you make assessments –
you make decisions –
you go forward –
in uncertainty