I believe that the social ideas of anarchism: autonomous groups, spontaneous order, workers’ control, the federative principle, add up to a coherent theory of social organisation which is a valid and realistic alternative to the authoritarian, hierarchical and institutional social philosophy which we see in application all around us. Man will be compelled, Kropotkin declared, “to find new forms of organisation for the social functions which the State fulfils through the bureaucracy” and he insisted that ”as long as this is not done nothing will be done.” I think we have discovered what these new forms of organisation should be. We have now to make the opportunities for putting them into practice.

One of the remark­able insights of com­puter sci­en­tists and social sci­en­tists and nat­ural sci­en­tists in the com­puter age is an under­stand­ing of how great com­plex­ity and diver­sity can be gen­er­ated by pop­u­la­tions of sim­ple agents fol­low­ing sim­ple rules. Just as schools of fish and flocks of star­lings cre­ate sweep­ing artis­tic dis­plays by pur­su­ing sim­ple indi­vid­ual rules, so the rich tapes­try of city life emerges from sim­ple every­day inter­ac­tions. The ideas of net­work the­o­rists lend them­selves to talk of self-organization, non-hierarchical struc­tures, and infor­ma­tional cas­cades. Com­puter sci­en­tists take ideas such as the “Game of Life”, the stun­ning images of frac­tal shapes, and the rich behav­iour of net­works to illus­trate how com­plex­ity arises from sim­plic­ity. From spin-glasses in mag­nets to the sort­ing and emer­gence of pat­terns revealed by Schelling and his intel­lec­tual descen­dants, sim­ple “micro­mo­tives” give rise to sur­pris­ing and intri­cate pat­terns of “mac­robe­hav­iour”. Such agent-based think­ing seems at first to mesh per­fectly with Jacobs’s closely observed stud­ies of city life. She famously focused her pierc­ing, ana­lyt­i­cal eye on the details of every day life in large cities, and used her obser­va­tions to chal­lenge and then tri­umph over the grand visions and arro­gance of top-down city plan­ners. It’s the bottom-up nature of her approach that inspires: the plan­ners are try­ing to impose pat­terns on pop­u­la­tions from above but they miss the rela­tion­ship between the large and the small. It is tempt­ing, then, to take the descrip­tions of Jacobs’s cities and encode them in algo­rithms: agent-based sim­u­la­tions of the effects of block size on pedes­trian traf­fic pat­terns seem almost man­dated, so obvi­ous a next step do they seem from Jacobs’s chap­ter on the topic.