Right definition of “discursus."

I was puzzled to find out the definition of “discursus” incidentally in Readers Plus English Japanese Dictionary, one of the best-selling English Japanese dictionaries, which is published by Kenkyusha, a well-reputed foreign language dictionary publisher in Japan.

It defines ‘discursus’ as;

n. 理路整然たる討議、説明 (logically consistent and well-organized discussion or explanation), while it defines ‘discursive’ as; a. digressive. One’s sentences and stories passing from one thing to another; ranging over a wide field.

To me, it’s strange that ‘discursus’ and ‘discursive” both of which are considered to be cognates derived from Latin `discurro’ meaning ‘running about’ come up in the reverse meaning: ‘discursus= logically consistent and well-organized” and ‘discursive =digressive, loose thinking.’

So I consulted with other English Dictionaries.

All CED, OED, Merriam-Webster define “discursive’ in the same way as “digressive; Passing from one thing to another; ranging over a wide field," but none of them provides definition of ‘discursus.’

Spellchecker keeps trying to correct “discursus” into “discourse” while I’m typing this question.

However, Wikitionary and Dictionary.com. carry the heading of ‘discursus’ with the same definition as an uncountable noun; (Logic) Argumentation; ratiocination; discursive reasoning.

Google NGram shows that compared with a notable rise of the currency of ‘discursive’ (0.000669585% in 2007), the incidence of ‘discursus’ is negligibly low (0.0000009975%).

Do you think the definition of Readers Plus English Japanese Dictionary of “discursus” is appropriate? Depending on your input, I’d like to request the editor of the dictionary to re-edit the definition of the word.

Solution 1:

Discursus, (Ngram) is a formal, uncommon term used with the below definitions (actually a Latin term). I think that your Reader Plus Japanese Dictionary gives an appropriate definition of it:

• n. (Logic) Argumentation; ratiocination; discursive reasoning.

• n. argument.

Discursus:

• In his five-volume Discursus academici de iure publico (1615–1623), Arumaeus pioneered public law as a distinct field of study. Influenced by Dutch humanism, his methodical analysis of the constitutional law of the Holy Roman Empire focused no longer on Roman law but on Imperial sources of public law, such as Imperial basic laws and electoral capitulations.

Discourse: as you note is the more commonly used term which derives form 'discursus':

• n.
  1. A formal, lengthy discussion of a subject, either written or spoken.
  2. Archaic The process or power of reasoning.

Discursive (adj.) [Medieval Latin discursvus, from Latin discursus], means also 'disgressive' and , I think, it is clearly related to its Latin origin.

• 1. Covering a wide field of subjects; rambling.
  2. Proceeding to a conclusion through reason rather than intuition.

Source:http://dictionary.reference.com/browse/discursus Source:http://www.finedictionary.com/Discursus.html