Furthermore, in the Church’s teaching, ownership has never been understood in a way that could constitute grounds for social conflict in labour. As mentioned above, property is acquired first of all through work in order that it may serve work. This concerns in a special way ownership of the means of production. Isolating these means as a separate property in order to set it up in the form of “capital” in opposition to “labour”-and even to practise exploitation of labour-is contrary to the very nature of these means and their possession. They cannot be possessed against labour, they cannot even be possessed for possession’s sake, because the only legitimate title to their possession- whether in the form of private ownerhip or in the form of public or collective ownership-is that they should serve labour, and thus, by serving labour, that they should make possible the achievement of the first principle of this order, namely, the universal destination of goods and the right to common use of them. From this point of view, therefore, in consideration of human labour and of common access to the goods meant for man, one cannot exclude the socialization, in suitable conditions, of certain means of production. In the course of the decades since the publication of the Encyclical Rerum Novarum, the Church’s teaching has always recalled all these principles, going back to the arguments formulated in a much older tradition, for example, the well-known arguments of the Summa Theologiae of Saint Thomas Aquinas.