When we review the field of history in the vast stretch of time from the beginning of Christianity to our own day, the various heresies that have from time to time appeared, seem clearly and distinctly marked off from the environment of the orthodox faith. We seem to be able to draw a geometrical line around about their respective areas, sharply dividing the camp of truth from that of error, separating the light from the darkness. But in this we are deceived; it is an illusion caused by distance. The distinction appears so clear, so definite only because we stand on the eminence of the present, from whose vantage ground we see, in large outline, the massed movements of peoples in the vast panorama of the past. A closer study, placing us in intellectual contact with these epochs, enables us to observe that never, in any period of history, were the dividing lines between truth and error defined with such geometrical exactness [not that truth in reality was not clearly and distinctly formulated in the definitions of the Churc] but because in its acceptation and its exterior profession by the generations interested in these definitions, more or less confusion and looseness characterized their manner of taking them.
Error in society is like a stain upon some precious tissue. It is easily distinguished, but it is very difficult to define its limits. These limits are as indefinite as the twilight which merges the departing day into the coming night or the dawn which blends the shadows of the spent darkness with the newborn light. So do the limits between error and truth in the actual affairs of men mingle in shadowy confusion. Error is a somber night; its limits fringe away from it like a huge penumbra, which is sometimes taken for the shadow itself, faintly brightened by some reflections of the dying light, or rather by the luminary yet enveloped and obscured by the first shades of evening.
So, too, all error clearly formulated in Christian society is, as it were, surrounded by an atmosphere of the same error, but less dense, more rarefied and tempered. Arianism had its Semi-Arianism, Pelagianism its Semi-Pelagianism, Lutheranism has its Semi-Lutheranism, which is nothing else than Catholic Liberalism. This is what the Syllabus terms modern Liberalism, that is, Liberalism without the boldness of its unvarnished first principles and stripped of the horrors of its last consequences; it is the Liberalism of those who are still unwilling not to appear to be Catholics or at least not to believe themselves Catholics. Liberalism is the baneful twilight of the truth beginning to be obscured in their intelligence, or heresy which has not yet taken complete possession.
On the other hand we should not fail to note that there are those who are just emerging from the darkness of error into the twilight of truth. This class has not fully penetrated into the domain of truth. That they will ever enter the city of light depends upon their own sincerity and honesty. If they earnestly desire to know the truth in its fullness and seek it with sincere purpose, God's grace will not fail them. But they are in a dangerous position. On the borderland between the realms of light and darkness the Devil is most active and ingenious in detaining those who seem about to escape his snares, and spares nothing to retain in his service a great number of people who would truly detest his infernal machinations if they only perceived them. His method in the instance of persons infected with Liberalism is to suffer them to place one foot within the domain of truth provided they keep the other inside the camp of error. In this way they stand the victim of the Devil's deceit and their own folly. In this way those whose consciences are not yet entirely hardened, escape the salutary horrors of remorse; so the pusillanimous and the vacillating, who comprise the greater number of Liberals, avoid compromising themselves by pronouncing themselves openly and squarely; so the shrewd, calculating [according to the measure of expediency-----how much time they will spend in each camp], manage to show themselves the friends and allies of both; so a man is enabled to administer an official and recognized palliative to his failings, his weaknesses, and his blunders. It is the obscurity that rises from the indefiniteness of clearly defined principles of truth and error in the Liberalist's mind that makes him the easy victim of Satan. His boasted strength is the very source of his weakness. It is because he has no real solid knowledge of the principles of truth and error that he is so easily deluded into the belief of his own intellectual superiority. He is a mental haze-----a fog which hides from him the abyss into which his vanity and pride, cunningly played upon by Satan, are invariably drawing him.