grammaticality - What does "in which" mean in this sentence?

I'm unable to understand this sentence.

In which we try to explain why we consider artificial intelligence to
be a subject most worthy of study, and in which we try to decide what
exactly it is, this being a good thing to decide before embarking

In the above sentence, I have two questions:

1. What does in which mean here?




2. Why is it this being ... rather than this is in the last part?

Answer

Can't comment yet, but: There are two questions. The guidelines suggest focusing on one question. I'll try to answer, anyway, for the reputation.

That example sounds like the abstract of a research paper, in fact a book [0].
I deem the style rather colloquial (e.g. "we try", "good idea"), which is common for researchers who are not primarily linguists, I dare to say. Although, "in which" is aimed at a formal tone. (I doubt it's a parody, more like tradition or homage).

To start with "In which" draws a connection to the matter of the title. Here, it means as much as "here" ("in" denotes direction). This usage is highly idiomatic, because "which" normally introduces a subordinate clause, not a substantive clause. Comparison to "wherein" suggests we are dealing with an adverb, hence an adverbial clause.

The latter subordinate clause "this being a good idea" is superfluous, because we expect to be presented with positive work. However, repetition is a valid stylistic device.

Subordinate clauses don't require a verb. "being" is used as participle [1], so "is" is not directly an alternative. That construction is called Participle Clause and, because of the weak noun "this", Nominative Absolute [2]. Using "is" is possible, but it would turn the sub clause into a main clause, or require a connective like "because". Frankly, it's a contraction to keep the text shorter.

[0] Russel & Norvig: Introduction to AI: A Modern Approach

[1] https://en.wikipedia.org/wiki/Participle

[2] https://en.wikipedia.org/wiki/Nominative_absolute

PS:

I don't think I understand this sentence completely

That's what English Language Learners SE is for; which is probably why perfectly good answers are posted as comments instead.