Filled with this idea, he proposed to Lewis XIII, in his dedication _Of the Rights of War and Peace_, to compose the differences of the Churches, and direct the age in which he lived how to terminate them in conformity to the sentiments of that time, when all allow that Christianity was in its purity. He imagined the alliance between France and England would facilitate the execution of a project worthy of such mighty Kings: he had it so much at heart, that he thought himself destined to labour in it from his mother's womb[643]. "It is a vocation, says he to his brother, which God has given me.--I have many witnesses, he writes to Duraeus[644], who knew me in my native country, and can attest not only how much I have desired, but also how much I have laboured to lessen the disputes among Christians, in order to promote gradually the restoration of unity. I might even appeal to yourself, in relation to what has since been done both in Germany and Sweden.--I shall never cease, he says to his brother[645], my utmost endeavours for establishing peace among Christians; and if I should not succeed, it will be honourable to die in such a pious enterprize." He had the consolation to be seconded in his pacific projects by Duraeus, a Clergyman in Sweden, with whom he cultivated a correspondence for advancing the coalition of Christians[646]. "What you labour in with so much zeal is precisely what I have been employed about since I began to have any relish for divine things. Experience teaches me how many difficulties we must expect both from Statesmen and Divines bigotted to their own opinions, and averse to those of others: but all these obstacles ought not to prevent our undertaking such a good work: if we do not succeed, we shall at least enjoy the satisfaction of having entertained very sublime ideas. For my part, as I have done it already, so I shall still continue to recommend to the High Chancellor your piety, your learning, your good intentions, and your zeal, to which I ardently wish success; and the accounts of your progress from time to time will give me the greatest pleasure.--Duraeus's enterprize is attended with particular difficulties at this time, he writes to Berneggerus[647]: but things as difficult have often had a happy issue: besides, it affords much satisfaction to a man's conscience to have attempted what is highly useful, even though he should fail of success." Duraeus meeting with great obstacles, Grotius consoles him on that head, in a letter of the 21st of November, 1637. "What gives me hopes, he says, is your constancy, and the countenance of the High Chancellor. I have conferred on this subject with the two English Ambassadors, the Earl of Leicester and Lord Scudamore: they are of my opinion, that the present time, while Europe is engaged in war, is not favourable for convoking a general assembly of Protestants."