Could you please elaborate as to how/why it's not correct?
The essay being referred to was written in the 1845 when Newman was still an Anglican. And it was an essay about what the Church had been doing for 2,000 years.
Cardinal Newman - Essay on the development of doctrine
It is the characteristic of our minds to be ever engaged in passing judgment on the things which come before us. No sooner do we apprehend than we judge: we allow nothing to stand by itself: we compare, contrast, abstract, generalize, connect, adjust, classify: and we view all our knowledge in the associations with which these processes have invested it.
Of the judgments thus made, which become aspects in our minds of the things which meet us, some are mere opinions which come and go, or which remain with us only till an accident displaces them, whatever be the influence which they exercise meanwhile. Others are firmly fixed in our minds, with or without good reason, and have a hold upon us, whether they relate to matters of fact, or to principles of conduct, or are views of life and the world, or are prejudices, imaginations, or convictions. Many of them attach to one and the same object, which is thus variously viewed, not only by various minds, but by the same. They sometimes lie in such near relation, that [Pg 34]each implies the others; some are only not inconsistent with each other, in that they have a common origin: some, as being actually incompatible with each other, are, one or other, falsely associated in our minds with their object, and in any case they may be nothing more than ideas, which we mistake for things.
Thus Judaism is an idea which once was objective, and Gnosticism is an idea which was never so. Both of them have various aspects: those of Judaism were such as monotheism, a certain ethical discipline, a ministration of divine vengeance, a preparation for Christianity: those of the Gnostic idea are such as the doctrine of two principles, that of emanation, the intrinsic malignity of matter, the inculpability of sensual indulgence, or the guilt of every pleasure of sense, of which last two one or other must be in the Gnostic a false aspect and subjective only.