It is always interesting to find thinkers who in their later life completely reverse or at least significantly modify their thoughts in some manner. Catholic priest de Lamennais is an example of such a thinker. While he was originally quite conservative in his opinions, disparaging French Revolution as a destroyer of traditional social and religious values, later on he would become a devout democrat, who would attempt to combine Christianity with a more liberal attitude toward affairs of state.
De Lamennais’ four-volume work, Essai sur l'indifference en matière de religion belongs still to the conservative period of his thinking. He is evidently inspired at least by de Bonald, whom he quotes approvingly several times in the first volume. But while de Bonald emphasised more the role of society, de Lamennais focuses on religion and especially the battle of philosophy against it.
Just like Chateaubriand earlier, at least in the first volume of his work de Lamennais does not even try to give a theoretical argument for the truth of religion in general and Catholic Christianity in particular, but he merely emphasises the practical need for religion. All humans strive for happiness, de Lamennais begins his apology. Yet, any being can be happy only if it satisfies laws of its own nature. A presupposition of this step in de Lamennais’ argument is that it must be possible that a human being can live without satisfying those laws - thus, fatalism must be simply false, de Lamennais says, because in a fatalist world we would all follow the laws of our nature and be happy, which is clearly not the case. Of course, one would easily make this argument collapse by choosing a completely different criterion for human happiness, such as pleasure and pain. Still, if we follow de Lamennais a step forward, we notice that to become truly happy we must know our place in the world, as designed by God, which is the job of religion.
Although individual human happiness is then one thing that de Lamennais uses in his defence of religion, it is especially the social benefits of religion - and particularly of Christianity - which he takes as his primary justification. All societies have been based on religion, and the longer the mores of a society have been in touch with the original religious consciousness, the longer it has lasted. Especially noteworthy in de Lamennais’ eyes is Christianity, which has stabilised and civilised Europe since the fall of Rome - and like Chateaubriand, de Lamennais is quick to compare the havoc caused by French Revolution with the education of Paraguay by Catholic priests.
From modern perspective one might note that Christianity has also been one of the forces stifling the development of society, but for de Lamennais this objection would not be valid, because he is still quite enthused about the conservative ideal of society, in which people are bound in a clear hierarchy, with different obligations and authorities assigned for different classes and genders. The philosophical counterpoint - the story of a pact made to form a society - is not favoured by de Lamennais, because it essentially confuses authority given by divine power with the force of majority to make others follow the laws dictated by them (of course, one might ask, what is meant to be the basis of divine authority, if not the supposed infinite force behind it).
One common enemy of Christianity and liberal politics de Lamennais find in slavery, which cannot really be tolerated. Yet, even here de Lamennais finds the policy of Catholic Church much more reasonable than the attempts of philosophical reformists - while latter try to change the state of African slaves in one enormous upheaval, Church tries to educate men to stop taking people as slaves. One might think that while such slow reform can often be pragmatically best option, it is quite peculiar that Church as the supposed mouth of God in the material world still renounces its own principles and advocates for a pragmatic solution.
The opponents of the Church de Lamennais divides into three categories, all of which are in some measure indifferent to the importance of religion. The first and clearest of these are atheists, who turn their back completely to God. While atheists would nowadays just deny the worth of religion, the supposed atheists of French Enlightenment might have been of different opinion and they could have admitted that religion is a useful tool for upholding society. Or at least de Lamennais says they have admitted this, mentioning at least Voltaire’s quip that he wouldn’t accept atheists as servants (we can ignore for now that Voltaire most likely wasn’t an outright atheist). De Lamennais finds in this attitude a sort of inconsistency, but upholding publicly what one deems as false is not a real contradiction, just a lie - and perhaps such an atheist could say that lies might be necessary and hence acceptable in the matters of society.
A further problem de Lamennais finds in the assumption that religion has been expressly invented as a deceit when creating the first society - such an invention would already require a society, for which it should have been basis. Yet, one need not either take religion as a conscious invention or suppose its divine origin. Instead, we might suppose that religions have grown accidentally from pre-social experiences and interactions of human beings and thus can fail to be true descriptions of the relation between humans and the supposed divinity, while still having an important role in the growth of civilization.
The second category of opponents includes deists, the foremost example of which for de Lamennais is Rousseau, as expressed by the speech of the Savoyard priest in the book Emile. Deists accept the existence of God, but they deny the need for any specific revelation, embodied expressly in the figure of divine mediator or Jesus. De Lamennais follows the official Biblical announcement that Jesus is the only true way toward knowing God and thus easily concludes that deists can really know nothing about God. Their only supposed source for the knowledge of God is human reason, but that is in de Lamennais’ eyes a fickle thing and something prone for errors, as shown by the fact that no two philosophers can agree on the nature of divinity. De Lamennais even uses Hume to show that reason can really say nothing about the existence of God, thus suggesting that deism just paves the way for straight atheism. The only content left for religion in deism is ethics, but this is especially something that cannot be decided by reason, de Lamennais insists, as shown by different customs of different nations. De Lamennais’ work reeks of an attitude where deism is not taken seriously, but is regarded as a mere lightweight substitute for religion - an attitude that doesn’t understand that religiousness can be embodied also in uncertain searching for something divine and not just in a faith founded on strong foundations.
Considering the Catholicism of de Lamennais, it is no wonder that the third opponent of true religion for him is protestantism in its various forms. If atheism tried to severe humans from God and deism from Jesus, protestantism attacks the relation between individual and church. One might think that this is a too severe judgement, because the protestants do have churches also, but it is more the unity of church de Lamennais is talking about. While Luther or Calvin might just have wanted to reform the original church, what they managed to bring about was a number of petty congregations, squabbling with one another. The problem in the whole reformist attitude, according to de Lamennais, is practically same as with deism - it tries to replace Catholic tradition with individual reason and conscience. What de Lamennais criticizes is the multiplicity of possible individual opinions on faith and God, while it is just this tolerance of individual opinions we might cherish as the true benefit derived from Reformation.