Section — Wouters, Manual of Moral Theology
§ VII. On Evil Associations
I. As regards societies properly so called, compare what was said in volume I, n. 509.
II. As regards the danger which associates create in a workshop, in military houses, etc., these occasions are commonly necessary. Let the confessor be greatly intent on this: that those living in the occasion frequent the sacraments.
III. Frequenting unbelievers, if the matter concerns familiar and habitual conversation, easily carries grave danger with it. Otherwise one must speak about rare and interrupted conversation. Nevertheless, the so-called circles are more dangerous, especially those of younger people, which are set up, for example, for the sake of playing games or cultivating musical art, whether young men and girls come together at the same time, or both Catholics and non-Catholics are enrolled in them.