Are Catholics allowed to read books that attack Catholicism without permission?

Are Catholics allowed to read and/or own books that attack Catholicism or argue in favor of other religions without permission, even if it is for a legitimate reason like strengthening their faith? I was reading an old moral theology book but I'm not sure exactly what it meant and if it was just talking about books that were on the Index of Forbidden Books. For example, a quote from John McHugh and Charles J. Callan, OP's *Moral Theology* (1929) [§849-§866. Dangerous Reading](https://archive.org/details/moraltheology0001john/page/320/mode/2up) : > **849. Dangerous Reading.**—There is a threefold prohibition against the reading of literature dangerous to faith. > > - (a) The *natural law forbids* one to read or hear read written matter of any description which one knows is dangerous to one’s faith, even though it is not dangerous to others and not forbidden by the law of the Church. For a similar reason one may not keep such material in one’s possession. Example: Titus and Balbus read the letters of a friend on Evolution. Titus finds nothing unsound in the letters, and is not troubled by reading them; but they fill the mind of Balbus with doubts and perplexities, as the subject is above him. This reading is naturally dangerous for Balbus, but not for Titus. > >- (b) The *law of the Church forbids* the use of certain kinds of writings or representations dangerous to faith (Canon 1399), as well as of those *individual* writings that have been denounced to the Holy See and placed on the Index, or forbidden by other ecclesiastical authorities. > >- (c) The law of the Church also *pronounces ipso facto excommunication* against those who make use of works written by unbelievers in favor of their errors (Canon 2318). > > [... omitted: the rest of the "Dangerous Reading" section (§850 to §866) which covers in great detail every aspect and every term mentioned in §849, such as §862 that spells out what "use" exactly means in §849c]