And first, what was the Inquisition?
The Inquisition forms no permanent or essential part of the organization of the Catholic Church. It was always a purely local tribunal, and the original appointment of its officers as quaesitores fidei, or inquisitors, seems to have been designed to prevent civil wars on the score of religion. The prevailing sentiment as well as the positive jurisprudence of the middle ages approved the punishment of heresy by temporal penalties. Indeed, such principles, abhorrent to us, seem to have come down out of the so-called dark ages far toward our own time. For full confirmation of this statement, you may read John Calvin's treatise in defence of persecuting measures, in which he maintains the lawfulness of putting heretics to death; and for illustration, you may peruse the account of his treatment of Castellio and Servetus, who found Calvin's reasoning of such peculiar strength that they did not survive its application; or his letter to Somerset, (1548:) "You have two kinds of mutineers: the one are a fanatical people, who, under color of the gospel, would set all to confusion; the others are stubborn people in the superstition of the Antichrist of Rome. These altogether do deserve to be well punished by the sword." (See Froude's History of England, vol. v.) Charming impartiality!
More than a hundred years afterward, Calvin's followers embodied his doctrine in their solemn confession of faith, wherein they say (Westminster Confession, ch. xxiii.) that "the civil magistrate hath authority, and it is his duty, to take order, that all blasphemies and heresies be suppressed."
Although inquisitors existed in Italy from the time of Innocent IV., their authority was so rarely exercised that it was scarcely known until Paul III., in the year 1545, organized the Congregation of the Inquisition, consisting of six cardinals. To these were added two more by Pius V. They formed a strictly ecclesiastical tribunal, charged with matters regarding the integrity of faith throughout the world; their duty being to examine and censure erroneous propositions, condemn and proscribe bad books, inflict ecclesiastical censures on clergymen convicted of error, and exercise a superintendence over the local tribunals of faith.
It still exists, acts, and exercises its ecclesiastical attributes.
But however powerful to suppress opinion or to exact obedience the Inquisition might be within the limits of its own special jurisdiction, we have never yet heard that any decree of any inquisition ever determined a question of faith, or, in other words, ever attempted to usurp the functions of a general council.
Even Riccioli, the original source, up to within a few years, of all accounts of the trial and sentence of Galileo, and himself one of the strongest theological opponents of the theory of the earth's motion, expressly protests against the assertion that any declaration whatever had been made on the subject by the church itself. He says: "The Sacred Congregation of Cardinals, taken apart from the Supreme Pontiff, does not make propositions to be of faith, even though it should actually define them to be of faith, or the contrary ones heretical. Wherefore, since no definition upon this matter has as yet issued from the Supreme Pontiff, nor from any council directed and approved by him, it is not yet of faith that the sun moves and the earth stands still by force of the decree of the Congregation; but at most and alone, by the force of the sacred Scriptures to those to whom it is morally evident that God has revealed it. Nevertheless, Catholics are bound, in prudence and obedience, at least so far as not to teach the contrary."
And yet, plain as is this distinction, men of professedly theological acquirements, for the sake of inflicting a wound on the church, systematically ignore it whenever they have "a point" to make with the Galileo story.
And the distinction is not only plain at the present day, but was expressly made at the time of Galileo's trial. "It was not in the power of the holy office to declare it (Galileo's scientific theory) or any other doctrine heresy; it would take an OEcumenical Council for that." (Letter of September 4th, 1632: Cardinal Magalotti to Galileo.) Even Descartes, six months after the trial, remarks that the decision of the Inquisition had received the ratification of neither pope nor council.