Three conditions are necessary if a question is to be considered as one of devotion: first, it must be edifying; second, it must be probable and attested by popular report or the testimony of the faithful; third, it must touch on nothing contrary to faith.

When these conditions are fulfilled, it is fitting neither persistently to condemn nor to approve, but rather to appeal to the church.
For example, the conception of the very holy Virgin, indulgences, relics, are matters of faith and not of devotion.

A relic may be worshipped in one place or another, or in several places at once.
Recently the Parlement of Paris disputed concerning the head of Saint Denys, worshipped at Saint-Denys in France and likewise in the cathedral at Paris.

This is a matter of devotion.[1133] [Footnote 1133: Gallia Christiana, vol.vii, col.142.Jean Juvenal des Ursins, year 1406.] Whence it may be concluded that it is lawful to consider the question of the Maid as a matter of devotion, especially when one reflects on her motives, which are the restitution of his kingdom to her King and the very righteous expulsion or destruction of her very stubborn enemies.
And if there be those who make various statements concerning her idle talk, her frivolity, her guile, now is the time to quote the saying of Cato: "Common report is not our judge." According to the words of the Apostle, it doth not become us to call in question the servant of God.
Much better is it to abstain from judgment, as is permitted, or to submit doubtful points to ecclesiastical superiors.

This is the principle followed in the canonisation of saints.