Marx was particularly attracted to the comprehensive nature of Proudhon's writings up to 1845 and the latter's willingness to make larger connections from smaller observations.[7] In his book What Is Property? Proudhon emphasized the social relationships emerging from private property, and the tendency of economic development to produce a propertyless proletariat in ever increasing numbers—ideas which Marx found compelling.[7] Marx's praise of Proudhon was not limitless, however, as he felt Proudhon did not fully grasp the way in which wages and money, for example, were themselves forms of private property.[8]