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times there are cities of complex activities and cities of specialized activities, industrial cities and commercial cities.^ ^ It might even be said that its activity {function) is one of the most variable characteristics of the city.
II. Let us pass next to definitions based upon multiple char- acteristics. Most commonly they distinguish the city by a multi- plicity of characteristics which are of the same nature. Thus M. Pirenne defines the city by means of a group of morphological characteristics/® and various contemporary economists define it by means of a group of functional characteristics.^"^ But the characteristics employed by the definition may also be of an unlike nature. The definition will then be based both upon the morphological and upon the functional characteristics of the aggregation.** But these definitions, being merely amalgama- tions of numerous simple definitions, already set forth, are subject to the same criticisms.
" See, for all this, my article, "La distribution geographique des industries," Revue intemationale de sociologie, July, 1908.
" The city, he says, is distinguished in a level country by its gates, the churches, and the density of the population. See, "L'origine des constitutions urbaines," Revue historique, t. LVII, 64.
" For example, by the coexistence of industrial, commercial, and political activities.
"In 1 80 1 the court at Rennes defined the city as an aggregation having "a numerous population, with which are connected public institutions for the har- mony of general association and the commercial needs" (cited by Ramalho, "Des villes, bourgs et villages," in the Revue generale d' administration, 1901, t. I, 291). Geddes, "Civics as Concrete and Applied Sociology," in Socio- logical Papers of the Sociological Society of London, 1905, II, 67 ff., 88 ff., defines the city as composed of three elements : people (individuals and insti- tutions), affairs (activities), and places. Von Below (see Burger, in Conrad- 'schen Handworterbuch der Staatswissenschaften, II, 11 81) characterizes the mediaeval city both by the fortification and by the market. Likewise Heil, Die deutschen Stddte im Mittelalter, pp. 25-27. Flach, Origines de I'ancienne France, II, 329, defines the city at the same time by the material defense, the religious protection, and the commercial activity. But the possession of a market with the special right attached thereto was far from characterizing all the cities. See a criticism of these definitions by Hassert, Die Stddte geogra- phisch betrachtet, 1907, pp. 4-6.
