El principio de subsidiariedad de la “Rerum Novarum” a “Fratelli tutti”: ¿hacia una nueva forma de sociedad civil para la solidaridad y la justicia social?

The principle of subsidiarity, which is based on the idea that what, by rule and competence, the lower organ (or body) can do by it-self, it should and that it is the responsibility of the higher organ (or body) only in exceptional cases, is not an expression of modern civilisation. Although, it was first explicitly affirmed in the Church's social doc-trine as a cardinal principle of the way of being and acting of the institutions of civil society (Pius XI and John Paul II). The innovative aspects of the introduction of the principle of subsidiarity are very strong, as it represents the concrete possibility of giving citizens - in the new configurations of civil society - an active role in the realisation of the collective good, which translates into solidarity and social justice. The question that arises is: in the neoliberal capitalist world, is the application of the principle of subsidiarity really possible? This contribution will try to find some answers, though not exhaustive, to this question. Moreover, it will try to add others that need to be answered in order to think humanity through its forms of expression of solidarity.