English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

It is a striking fact from reverse mathematics that almost all theorems ofcountable and countably representable mathematics are equivalent to just fivesubsystems of second order arithmetic. The standard view is that thesignificance of these equivalences lies in the set existence principles thatare necessary and sufficient to prove those theorems. In this article I analysethe role of set existence principles in reverse mathematics, and argue thatthey are best understood as closure conditions on the powerset of the naturalnumbers.

Set existence principles and closure conditions: unravelling the standard view of reverse mathematics