In this work, we present some traits of the socio-political and economic thought of Giuseppe Toniolo, who lived in Italy at the turn of the XIX and XX century, with special reference to the contribution that the Italian economist and sociologist gave to the definition and implementation of the principle of subsidiarity and to the ethical foundation of economic science. After outlining the definition of the subsidiarity principle in the first paragraph, we sketch the historical background in which Toniolo lived (...) and operated. We then focus on the ethical factor and on the concept of subsidiary State emerging from Toniolo’s writings. Finally, we present some of the main elements of Toniolo’s legacy with reference to the current economic and socio-political debate. (shrink)