How did "discursive" come to have two opposite meanings?

Question

I was reading something on parental mediation of children's videogame play when I first came across the word discursive:

We explain how restrictive, co-use, and active mediation are constituted by gatekeeping, discursive, diversionary, and investigative activities.

All of these are well explained later in the article. For example:

Discursive activities are dialogues that enable parents and children to share perspectives on various aspects of videogames, where parents air concerns while inculcating values and proffering advice on managing the negative aspects of videogames.

But I couldn't wait until the writer explained what discursive meant, so I peaked through multiple dictionaries only to know the word has two interesting, somewhat unrelated, meanings:

1.(of speech or writing) Tending to digress from the main point; rambling.

2.(philosophy) Using reason and argument rather than intuition.

Wikitionary

Those seemed to me very unrelated so I went on further to vocabulary.com And here I quote:

If people accuse you of rambling from topic to topic in your speech or writing, they may say you have a discursive style — with changes in subject that are hard to follow. But it's okay because unicorns are shiny. The adjective discursive is often used to describe speech or writing that tends to stray from the main point, but the word can also have almost the opposite meaning. Discursive can also be used to describe an argument based on reason instead of intuition: "Her discursive dissertation on Colonial American women was well-argued and well-reasoned. Her professors were most impressed with her work."

This confirmed the idea that there's something unusal about this word being used for two opposite meanings. I don't know how the two meanings developed or what justifies the word being used this way.

Answer 1

Both senses of the word come from the Latin word discursivus and they both entered English at about the same time (the OED has earliest citations of 1599 and 1595 for your first and second senses respectively).

So we need to look at the Latin, which is well explained by this source:

discursus: a discourse or conversation; adj., discursivus, -a, -um: discursive, having the characteristics of a discourse. Note that the classical Latin meaning, digressive or running about (from dis and curro), gave place in later Latin to a sense of more formal discourse in which concepts are conjoined or indeed “run through,” usually analytically, as in a treatise or dissertation. The scholastics contrast knowledge that is innate or implanted and knowledge of immediate apprehension with discursive or dianoetic knowledge, which is gained by ratiocination.
_{Dictionary of Latin and Greek Theological Terms}

Answer 2

The second meaning you cite (that of following reason rather than intuition) is clearly a specialised meaning in the domain in the philosophy: it is marked as philosophy in Wiktionary, in Merriam-Webster, and in ODO, and it doesn't appear in learners' dictionaries such as Cambridge. It is even marked as "archaic" in ODO.

ODO's three definitions are:

• 1. Digressing from subject to subject; 1.1 fluent and expansive.
• 2. Relating to discourse or modes of discourse.
• 3. Philosophy: archaic Proceeding from argument or reason rather than intuition.

M-W's definitions are:

• 1a. Moving from topic to topic without order. 1b. Proceeding coherently from topic to topic.
• 2. philosophy marked by a method of resolving complex expressions into simpler or more basic ones : marked by analytical reasoning
• 3. of or relating to discourse: discursive practices.

Cambridge's definitions are:

• involving discussion.
• formal talking about or dealing with subjects that are only slightly connected with the main subject for longer than necessary.

Thus, "discursive" is usually either an adjective relating to the word "discourse", or it is a way that someone has spoken or discoursed at length: you have to tell from the context whether you think the person is being accused of rambling off topic.

The philosophical meaning can be ignored unless you are reading in that field.