since it consists in the linking together of truths, is entitled to connect also those wherewith experience has furnished it, in order thence to draw mixed conclusions; but reason pure and simple, as distinct from experience, only has to do with truths independent of the senses.  And one may compare faith with experience, since faith (in respect of the motives that give it justification) depends [74] upon the experience of those who have seen the miracles whereon revelation is founded, and upon the trustworthy tradition which has handed them down to us, whether through the Scriptures or by the account of those who have preserved them.  It is rather as we rely upon the experience of those who have seen China and on the credibility of their account when we give credence to the wonders that are told us of that distant country.  Yet I would also take into account the inward motion of the Holy Spirit, who takes possession of souls and persuades them and prompts them to good, that is, to faith and to charity, without always having need of motives.

2.  Now the truths of reason are of two kinds:  the one kind is of those called the ‘Eternal Verities’, which are altogether necessary, so that the opposite implies contradiction.  Such are the truths whose necessity is logical, metaphysical or geometrical, which one cannot deny without being led into absurdities.  There are others which may be called positive, because they are the laws which it has pleased God to give to Nature, or because they depend upon those.  We learn them either by experience, that is, a posteriori, or by reason and a priori, that is, by considerations of the fitness of things which have caused their choice.  This fitness of things has also its rules and reasons, but it is the free choice of God, and not a geometrical necessity, which causes preference for what is fitting and brings it into existence.  Thus one may say that physical necessity is founded on moral necessity, that is, on the wise one’s choice which is worthy of his wisdom; and that both of these ought to be distinguished from geometrical necessity.  It is this physical necessity that makes order in Nature and lies in the rules of motion and in some other general laws which it pleased God to lay down for things when he gave them being.  It is therefore true that God gave such laws not without reason, for he chooses nothing from caprice and as though by chance or in pure indifference; but the general reasons of good and of order, which have prompted him to the choice, may be overcome in some cases by stronger reasons of a superior order.