The treatment of this subject by the learned historian of
Christianity, E. de Pressense, in his "Histoire du Dogme" (Paris,
1869), under the heading "Ubi Christus, ibi Ecclesia," may serve
as an illustration of the complete absence of anything like a
definition of what is understood by the word heresy. Here is what
he says in his introduction (p. 3):

"Je sais que l'on nous conteste le droit de qualifier ainsi
[that is, to call heresies] les tendances qui furent si
vivement combattues par les premiers Peres. La designation
meme d'heresie semble une atteinte portee a la liberte de
conscience et de pensee. Nous ne pouvons partager ce scrupule,
car il n'irait a rien moins qu'a enlever au Christianisme tout
caractere distinctif." [see Footnote]

[Footnote: "I know that our right to qualify thus the
tendencies which were so actively opposed by the early
Fathers is contested. The very use of the word heresy
seems an attack upon liberty of conscience and thought.
We cannot share this scruple; for it would amount to
nothing less than depriving Christianity of all
distinctive character."

And though he tells us that after Constantine's time the Church
did actually abuse its power by designating those who dissented
from it as heretics and persecuting them, yet he says, when
speaking of early times:

"L'eglise est une libre association; il y a tout profit a se
separer d'elle. La polemique contre l'erreur n'a d'autres