Royal Society. 417 
<?ays will be fubftradled in 40 years, and thefe 40 years will 
each of them be Anni equabiles^ confifting of 355 days 5 as our 
common and ordinary years do, without any alteration in the 
whole year. 
The Credibility of Human Teftimony. Phil. Tranf. N". 1^6* 
P- 3 59- 
MORAL certitude abfolute, is that, in which the mind of 
man entirely acquicfces, requiring no further affurance : 
As if one, in whom a man abfolutely confides, ihould brinpj 
him word of 1200 /. accruing to him by gift, or by the arrival 
of a fhip, and for which he therefore would not give the leafb 
valuable confideration to be infured : Moral certitude incom- 
plete has its feveral degrees, to be eftimated by the proportion 
it bears to the abiolute 3 as if one, in whom a perfon has that 
degree of confidence, as that he would not give above one in 
fix to be enfured of the truth of what he fays, fhall inform him, 
as above, concerning 1200 /. he may then reckon thit he has 
as good as the abfolute certainty of icuo /. or Hve fixths of ab- 
folute certainty for the whole iiim : The credibility of any re- 
porter is to be rated, i. By his integrity or fidelity 5 and 
2. By his ability • and a double ability is to be conlidered 5 
both that of apprehending v^hat is delivered, and alfo of retain- 
ing it afterwards, till it be tranimitted. 
What follows concerning the degrees of credibility is divided 
into four propofitions 5 the two hrft refpec^t the reporters of the 
narrative, as they either traniinit fucceirively, or atteft concur- 
rently 5 the third the fubjed of it, as it may confift of levcral 
articles ; and the fourth joins thofe three confiderations together, 
exemplifying them in oral and written tradition. 
\Prop. I. Concerning the credibility of a report, made by fingle 
fucceffive reporters, who are equally credible : Let their re- 
ports have each of them' five fixth's of certainty 5 and let the 
firft reporter give me a certainty of icoo /. in 1 200 /. it is plain 
that the fecond reporter, who delivers that report, will give me 
the certainty but of J of that 1000/. or the f- off- of the full cer- 
tainty for the whole 1200/5 and lo a third reporter, who has it 
from the fecond, would have delivered me bur the f of I- of !• 
of the full certainty, ^c. That is if ^ be put for the fl-iare of 
alTurance a fingle reporter gives me, and c for that which is 
wanting to make that affuiance complete 3 and I therefore be 
fuppofed to have — - — of certainty from the firft reporter. 
Vol. III. ^ G g g I fliall 
