Are you interested in where the three pillars of sustainability came from?
Summary of the article titled Three pillars of sustainability: in search of conceptual origins from 2018 by Ben Purvis, Yong Mao and Darren Robinson, published in the Sustainability Science journal.
Since we are investigating the future of cities, I thought it would be interesting to see how the three pillars of sustainability – social, economic and environment – came about. This article investigates the origins of sustainability and the gradual emergence of these pillars due to critics.
As the most important things, I would like to highlight 3 aspects:

Sustainable ideas have been emerging since the 17th century but gained more aspects during the 20th century to include economic, environmental and social aspects and economic growth can be a solution to environmental and social challenges.
Sustainable development was clearly defined in the 1987 Brundtland report as development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
Even though the origins of the three pillars are unclear, each of them is vital for sustainability and a clear understanding is crucial for proper implementation and decreased political nature.

You can find the article through this link.
Abstract: The three-pillar conception of (social, economic and environmental) sustainability, commonly represented by three intersecting circles with overall sustainability at the centre, has become ubiquitous. With a view of identifying the genesis and theoretical foundations of this conception, this paper reviews and discusses relevant historical sustainability literature. From this we find that there is no single point of origin of this three-pillar conception, but rather a gradual emergence from various critiques in the early academic literature of the economic status quo from both social and ecological perspectives on the one hand, and the quest to reconcile economic growth as a solution to social and ecological problems on the part of the United Nations on the other. The popular three circles diagram appears to have been first presented by Barbier (Environ Conserv 14:101, doi: 10.1017/s0376892900011449, 1987), albeit purposed towards developing nations with foci which differ from modern interpretations. The conceptualisation of three pillars seems to predate this, however. Nowhere have we found a theoretically rigorous description of the three pillars. This is thought to be in part due to the nature of the sustainability discourse arising from broadly different schools of thought historically. The absence of such a theoretically solid conception frustrates approaches towards a theoretically rigorous operationalisation of ‘sustainability’.
Connecting episodes you might be interested in:

⁠⁠⁠No.008R - What are the differences between sustainable and smart cities?⁠;
⁠⁠⁠No.036 - Interview with Magnus Moglia about urban regeneration and sustainability⁠;

You can find the transcript through ⁠⁠this link⁠⁠.
What wast the most interesting part for you? What questions did arise for you? Let me know on Twitter ⁠⁠@WTF4Cities⁠⁠ or on the ⁠⁠wtf4cities.com⁠⁠ website where the ⁠⁠shownotes⁠⁠⁠⁠ ⁠⁠are also available.
I hope this was an interesting episode for you and thanks for tuning in.
Music by ⁠⁠Lesfm ⁠⁠from ⁠⁠Pixabay