We come to the final major section of Pacem in Terris. In Part V Pope John offers a series of “pastoral exhortations.” Lay people should not retreat or withdraw from the world, but engage it, and bring Christ to it by means of their activities:
146. Here once more We exhort Our (daughters and) sons to take an active part in public life, and to work together for the benefit of the whole human race, as well as for their own political communities. It is vitally necessary for them to endeavor, in the light of Christian faith, and with love as their guide, to ensure that every institution, whether economic, social, cultural or political, be such as not to obstruct but rather to facilitate (human) self betterment, both in the natural and in the supernatural order.
I think repressive fatalism is such an obstruction. You know what I mean: the attitude that concedes that because human beings can never be perfect, we can never work to make things better. I think we have to enter the world with the intention of facilitating the best possible self of everyone we encounter, as well as the best possible expression of communal aspects. Of course sin will get in the way. Our government, swim club, or knitting circle will never be perfect, nor will it ever reach its full potential. But pessimism is as much a grave flaw as any other moral transgression we throw out there.