Here’s the details of the story, at motherjones.com In this post, I’m considering the moral implications of this firing, not the legal ones.
Morally, a Catholic school can and should require its teachers to avoid “manifest grave sin”, which would harm the students by bad example. Students often have a good opinion of at least some of their teachers; they admire and lookup to them. If a teacher treats an objective mortal sin as if it were moral and good, the understanding of morality of the students is harmed.
Ideally, the teachers in any Catholic school should be believing and practicing Catholics, who do not “obstinately persist in manifest grave sin”. That phrasing is from Canon 915, on refusing holy Communion to certain persons, because of a known grave sin. But the same thinking can be applied to other situations, in so far as manifest grave sin may harm by scandal. An employee or volunteer at a parish who is known to obstinately persist in manifest grave sin, should be removed from their position. Otherwise, it seems as if the Church is approving of the sin.
However, there are a few other considerations. Not every grave sin should result in the person being fired from any job. We are all fallen sinners. If every grave sin resulted in loss of employment, or inability to be hired, a large number of persons would be unemployed, and perhaps unemployable, and the economy would collapse. Similarly, if every teacher in every Catholic school were fired for those grave sins that are legal and unfortunately common (e.g. heresy, contraception, abortifacient contraception, and various sexual sins), there would not be enough teachers and the school system would collapse.
The above cited article makes a good point about the uneven standards as to which sins result in firing. Teachers are not fired for a wide range of grave sins. But they are fired for IVF. They are not fired for using abortifacient contraception, which probably results in more prenatal deaths than IVF. They are not fired for pre-marital sex or direct sterilization.
Morally, it is unjust to have such inequality in rules for teachers. If one teacher is fired for using IVF, then other teachers must be fired for grave sins that are similar in harm and scandal.
On the other hand, there is no moral obligation for every Catholic school to hire only Catholics, or to have only Catholics as students. A Catholic school can decide to hire non-Catholic Christians and non-Christians, who of course would not be required to adhere to Catholic doctrine. A Catholic school can decide to accept students who are not Catholic. The school can avoid scandal by teaching the students that we live in a pluralistic society, and not everyone agrees with Catholic teaching. The school can have a priest, or a nun, or a qualified layman teach classes in theology and morality, to further clarify the distinction between Catholic teaching and what is commonly accepted as normal in society.
I would still like some schools at every level to be available which are Catholic only. I’d like the Church to have, as a resource, some schools with only believing and practicing Catholic teachers and students. This type of school is a closed garden where souls can be nourished. But the newest laws and cultural biases in sinful secular society are making this type of school much harder to maintain.
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