His labours were characterized by a Church consciousness, a constant struggle against scholasticim and the specific elements of Latinism which had penetrated into our theology from the time of Metropolitan Peter Mohila. His ideal was Churchliness and spirituality (as opposed to scholastic-rationalism) in theological learning.
Vladyka Ilarion's constant theme was that: outside the Church there is no salvation, outside the Church there are no sacraments (mysteria).
When he had occasion to write a letter of reply (which appeared in "The Theological Herald", January, 1917) to Robert Gardiner, the secretary on the commission for the organization of a world conference of Christianity, Archbishop Ilarion expressed him unshakeable convictions with especial strength. Here are the more salient portions of that reply:
"I had the pleasure of receiving your kind letters, in one of which (that of September 13, 1916) you expressed the hope that I not only will read the brochures you had sent, but that I would inform you of my remarks (concerning them).
"With joy I am ready to converse with you on a subject so dear to me, the question about the Church. . ."
"According to your beliefs, all societies which call themselves Christian compose the one Church of Christ, but one which is lax in its unity. . .
"It is completely impossible to accept such a teaching about the Church since it (this teaching) is absolutely unknown in the ancient Church in which no lax understanding of the unity of the Church was known. . . The truth of Christianity, its great mystery – the incarnation of the Son of God – is acknowledged by all Christian confessions. This alone, however, cannot blend them into one Church. Even the demons, according to the Apostle James, believe (2:19) and, according to the testimony of the Gospel, they confessed their faith even as the Apostle Peter did (Matt. 16:16; 8:26; Mark 1:24; Luke 8:28)."
In the post-sobor period, before his arrest, Archbishop Ilarion was a most eloquent preacher and all the faithful of Moscow flocked to hear him. During this period of the bolshevik captivity he was one of the first supporters of His Holiness Patriarch Tikhon.
At the Church Sobor itself, he delivered perhaps the most brilliant address on the patriarchy. His address abounds with such words as: "The Russian Church was never without a first-hierarch, but our patriarchy was abolished by Peter I. In whose way was it? The coming together of the Church? But did we not have especially many sobors in the time of the patriarchs? No, our patriarchy was in the way of neither catholicity nor the Church. In whose way was it then?