First.

also: from what, and from which premises it is composed. And such a Demonstration our [predecessors] call A priori from the cause to the effect: and Propter quid reason why demonstration. And this is different from the Demonstration that is called A posteriori from the effect to the cause and Quia that it is: which is that which is taken from signs and universal causes, as I have declared above regarding the second mode of Knowledge.

FRAN. These are things that are easily understood: therefore, do not let it be a bother to continue.

GIOS. I will therefore place before you two definitions of Demonstration, one will be from the final cause, and the other from the material. You must therefore note: that just as we say, wishing to define the House by its end, which moves us to build it: that it is a thing that covers and defends us from the cold, from the rain, from the snow, and from the heat: since it is for this end that we build it. Or, taking the definition from the matter of which it is composed, we come to say: that it is a thing composed of stones, of mortar, of wood, and other similar things: so taking the definition of Demonstration from its end, we will say: that the Demonstration (as Aristotle declares it in the 1st [book] of the Posterior Analytics) is a scientific Syllogism: or it is a Syllogism of science: as it is more convenient for us to say: which truly causes in us, or brings forth Science, or the Knowledge that we have defined above.

CLAV. I understand this very well; I have no need of further explanation: therefore continue, for if I learn everything you say as easily as I have learned what you have said until now, things will go well.

GIOS. The definition of Demonstration, which is taken from the matter, Mr. Claudio: will be given in this way. The Demonstration is a Syllogism that is composed of true, primary, immediate premises, or [those] without any intermediary: and causes [that are] more notable; and more primary, and known than the conclusion. And although all these things are sought: it is also necessary that such premises are before, or precede the conclusion: and are its cause. So that from one and the other of these two definitions you can understand what enters into the Demonstration, and the end for which it was discovered.

FRAN. Truly, the first definition is clear to me: but the second leaves me somewhat doubtful: because I do not remember so well what is understood by true, primary, immediate premises: and causes more notable, and more primary than the conclusion. Therefore I pray you, that you explain these terms to us: for I believe that this is the place for it.

GIOS. Therefore, so that you may have good knowledge of these things, stand by to listen to me. I said above that the Premises must be true: because, having to make the conclusion known in such a way that it is impossible that it arises from any other place than the cause contained within them: it is highly necessary that such Premises be true: and consequently, the cause of the conclusion.

ADRI. In what manner [are they] the cause of the conclusion?

GIOS. I say cause, not only of the consequence: as happens in other Syllogisms by their form, which is required to happen: but the cause of the true being of the conclusion: which is proper to the demonstrative Syllogism: of which we are now speaking.

CLAV. This is understood very well.

GIOS. The premises must also be more notable than the conclusion: and must also precede it.

FRAN. What do you mean by this preceding: and by more notable?

GIOS. That they are not such in relation to us: but in relation to Nature itself: the knowledge of which does not always concur with ours.

FRAN. Please see that we understand you better.

GIOS. Note, therefore, that in respect to Nature, we must say that the causes with which she works [her] effects are more notable to her than those effects are, and consequently, that those effects in her knowledge go after the causes: just as they also precede in the act equally: since without any doubt she produces all effects by means of them. Whence, having respect to us, who do not operate those effects: by means of the sense, which shows them to us: those most of the time present themselves to our knowledge before the causes do: which, reasoning by means of such effects, we know in the last place. So that the order of our knowledge most of the time is found to be contrary to that of Nature. Which Nature, operating from that which she produces to that which follows: similarly by the intelligence that she has within herself: knows by means of the said order. But we, from that which follows, often proceed to that which comes before, for the reason stated.