In response to an essay by venture capitalist Marc Andreessen titled "The Techno-Optimist Manifesto" and as a corollary to e/acc effective accelerationism (which specifically promotes the accelerated development of general artificial intelligence and in turn was partly a criticism of the conservatism of Effective Altruism), Vitalik Buterin published an essay titled my techno optimism coining the term d/acc, or defensive accelerationism.
We need to build, and accelerate. But there is a very real question that needs to be asked: what is the thing that we are accelerating towards? The 21st century may well be the pivotal century for humanity, the century in which our fate for millennia to come gets decided. Do we fall into one of a number of traps from which we cannot escape, or do we find a way toward a future where we retain our freedom and agency? -- Vitalik Buterin, Nov 27, 2023
The "acc" in defensive accelerationism is a form of "techno optimism" in that it believes that technology can improve human civilization and we should pursue this outcome as quickly as possible (as opposed to decelerationists, such as AI "doomers", who think technology is more likely to damage humanity than improve it in the long run, or luddites, who would prefer we undo some of our technologies and return to relatively more primitive states).
The "d" stands for defensive and has dual meaning. One meaning is we should actively build technologies that protect human agency and are resistant to corruption, the other meaning applies to how we should carefully consider which technologies we choose to build because certain branches of technological development are likely to be dangerous. d/acc then explains that we should pursue the development of technology to improve human civilization as quickly as is safely possible while simultaneously developing technologies that improve the odds of our fluourishing.
The entire essay was published in a small printed booklet for Devcon7 attendees.