One especially harsh warning against the errors of gnosticism in Gaudete et exultate, 39 says:
Here we have to be careful. I am not referring to a rationalism inimical to Christian faith. It [i.e., gnosticism] can be present within the Church, both among the laity in parishes and teachers of philosophy and theology in centres of formation. Gnostics think that their explanations can make the entirety of the faith and the Gospel perfectly comprehensible. They absolutize their own theories and force others to submit to their way of thinking. A healthy and humble use of reason in order to reflect on the theological and moral teaching of the Gospel is one thing. It is another to reduce Jesus’ teaching to a cold and harsh logic that seeks to dominate everything.
Pope Francis prefers to speak and write in strong terms. In this case, at least, they're maybe not too strong. We can see fairly well what's at stake: "explanations" that "can make the entirety of the faith and the Gospel perfectly comprehensible" and "cold and harsh logic that seeks to dominate everything." Most (probably virtually all) Christian intellectuals would agree that these are each contrary to the orthodox tradition and faith, itself. And it's unlikely that there are many, either lay Catholics or formators or teachers, who would espouse any sort of formal gnosticism.
In a following paragraph, however, something familiar appears:
When somebody has an answer for every question, it is a sign that they are not on the right road. They may well be false prophets, who use religion for their own purposes, to promote their own psychological or intellectual theories.
What gnosticism undermines most, according to Francis, is the mystery of the faith and the dynamism of the Holy Spirit—not so much the content of the message of faith, but its interpretation and expression. "It is not easy to grasp the truth that we have received from the Lord. And it is even more difficult to express it." (43)
In effect, doctrine, or better, our understanding and expression of it, “is not a closed system, devoid of the dynamic capacity to pose questions, doubts, inquiries… The questions of our people, their suffering, their struggles, their dreams, their trials and their worries, all possess an interpretational value that we cannot ignore if we want to take the principle of the incarnation seriously. Their wondering helps us to wonder, their questions question us.” (44)
This is maybe the most challenging passage in Gaudete et exultate (along with paragraphs 57–59 on "New pelagians"). It plays into the impressions that many ascribe as intentional by Francis to elevate the "interpretational value" of heterodox formulations. Francis seems to recognize this, focusing explicitly on the "expression" of doctrine rather than doctrine itself. There is certainly a way, then, that such expression leaves open "the dynamic capacity to pose questions, doubts, inquiries." Faith and faithlessness, Ratzinger says, are not disconnected from one another; believers are constantly plagued by doubts, and unbelievers are, too. This dialectical situation is a natural means of expressing the power of the Gospel, and not de facto opposed to orthodoxy.
Doctrine itself, however, to whatever degree is warranted and appropriate, does create boundaries within which faithful Christians can think and question. At some point, doubts against the content of faith are doubts against faith, itself. This is a subject, in any case, that deserves more attention, and about which intelligent, faithful Christians should spend more effort to make key distinctions and insights.
Francis concludes the section on errors by writing:
May the Lord set the Church free from these new forms of gnosticism and pelagianism that weigh her down and block her progress along the path to holiness! These aberrations take various shapes, according to the temperament and character of each person. So I encourage everyone to reflect and discern before God whether they may be present in their lives. (62)