Il vérifie, non pas que cela augmente, mais pour comprendre.

Here, vérifie most naturally means checks rather than the stronger English verb verifies. In many contexts, French vérifier simply means to check, inspect, or make sure about something.

So a learner should not assume it always has the formal sense of prove true.

This is a contrastive structure meaning not ..., but ....

It is used to reject one idea and replace it with another:

• non pas X, mais Y = not X, but Y

Compared with plain pas, non pas sounds a bit more emphatic, careful, or literary. It often appears in written French or more formal speech.

Not in this sentence, or at least not directly.

A learner might first think of the pattern vérifier que... = to check that..., which is a very common French structure. But here, que cela augmente is part of the expression non pas que..., so it belongs to the contrast structure, not simply to vérifie.

That means the sentence is not straightforwardly saying He checks that it is increasing. Instead, it is rejecting that idea and moving toward another purpose or explanation.

Because non pas que... is a set structure meaning something like not that... or, depending on context, not because....

Here que introduces a full clause:

• que cela augmente = that it is increasing

So the pattern is:

• non pas que + clause

This is different from ordinary negation with ne...pas. It is not simply saying he does not check; it is correcting a possible interpretation.

Most likely yes.

After non pas que, French normally expects the subjunctive, because the clause presents an explanation or idea that is being rejected rather than asserted as a plain fact.

The tricky part is that with augmenter, the present indicative and present subjunctive forms are spelled the same in the third-person singular:

• indicative: cela augmente
• subjunctive: que cela augmente

So you cannot see the difference in spelling here, but grammatically the subjunctive is what a learner should expect after non pas que.

Because pour + infinitive is used when the subject of both actions is the same.

In this sentence, the person who checks is also the one who understands, so French uses:

• pour comprendre = in order to understand

If the subject were different, French would usually use pour que + subjunctive:

• Il vérifie pour qu'elle comprenne.
• He checks so that she understands.

So pour comprendre is the normal choice when he is the one doing both actions.

Cela and ça can both mean that or it, but they differ in register.

• cela is more neutral, careful, or written
• ça is more common in everyday spoken French

So cela fits the slightly formal tone created by non pas. In casual speech, many speakers might say ça instead.

The commas set off the contrastive insertion non pas ..., mais ....

They show that the speaker is interrupting the main statement to add a correction or clarification. In speech, you would usually hear small pauses around that part.

So the commas help the reader hear the structure more clearly.

Because this is not the ordinary verbal negation ne...pas.

Instead, non pas is a separate contrastive expression meaning not ... but rather .... It does not work the same way as standard negation around a verb.

Compare:

• Il ne vérifie pas. = He is not checking.
• Il vérifie, non pas X, mais Y. = He checks, not X but Y.

So the sentence is not negating vérifie completely; it is correcting what kind of checking, reason, or interpretation is involved.

It is understandable, but it sounds a little compressed and slightly awkward to many learners and probably to some native speakers too.

The main reason is that non pas que cela augmente and mais pour comprendre are not perfectly parallel in structure. French often sounds smoother when the two parts match more closely.

Depending on the intended meaning, a more natural version might be something like:

• Il vérifie, non pas parce que cela augmente, mais pour comprendre.
• Il vérifie, non pour voir si cela augmente, mais pour comprendre.

So the original sentence is useful for studying grammar, but in real usage a native speaker might well choose a clearer phrasing.