Non est non ens scire

Question

I was reading Niccolo Cabeo's Philosophia Magnetica (1627), p. 180 and found this line:

...quicquid reclamet Aristoteles: non est non ens scire.

The context is regarding experiments, and how some philosophers were deluding themselves by searching for causes or reasons for things, but those causes did not exist. (Specifically, it's a response to electricity, as some people tried to explain why chaff and straw were the only things attracted by amber, but in fact all materials were actually attracted.)

I think the translation would literally be:

There is no nothingness to know.

But a more relaxed (and possibly incorrect) translation could be:

There is nothing to know from nothing.

I haven't heard this quote from Aristotle before. What does it mean, and where is it from? (The second question might be better suited to e.g. history of math and science SE, question can be edited if anyone wants.)

Answer 1

I believe this may be from Aristotle's Posterior Analytics. In chapter 2, he wrote:

Ἀληθῆ μὲν οὖν δεῖ εἶναι, ὅτι οὐκ ἔστι τὸ μὴ ὂν ἐπίστασθαι, οἷον ὅτι ἡ διάμετρος σύμμετρος.

This has been translated into Latin in a way very similar to what you quoted:

Vera ergo oportet esse, quonian non ens scire non possumus; ut, diametrum esse costae commensurabilem.

It is, therefore, necessary that [the premises] be true, since we cannot know what doesn't exist; as, [for example], the diagonal must be commensurable with its side.

In fact, your line is actually closer to the Greek than the translation I quoted:

οὐκ ἔστι τὸ μὴ ὂν ἐπίστασθαι

non est non ens scire

Here, the participle phrase non ens corresponds to τὸ μὴ ὂν, i.e., what doesn't exist, or, in this context, what is contrary to fact.

As @brianpck pointed out in a comment, the combination, ἔστι + ἐπίστασθαι, is idiomatic (ἔστι + inf.), meaning it is possible to know.

Hence, it might be translated as "It's not possible to know what doesn't exist". That would explain the other Latin translation: non ens scire non possumus, "We cannot know what doesn't exist."

The context of this is a discussion of syllogisms, and the conditions necessary for a conclusion to be inferred from an argument's premises. The idea is that the conclusion cannot be known unless the premises are also true and knowable.