Learning Esperanto first may lead to faster proficiency in French, but it may not be good proficiency. This is because learning the words first through Esperant

Learning Esperanto first may lead to faster proficiency in French, but it may not be good proficiency. This is because learning the words first through Esperanto would ingrain some bad habits in the learner that will be hard to eradicate after he or she moves on to French. What I have in mind is the fact that French distinguishes between the vowels /ɔ/ and /o/, and between /ɛ/ and /e/. When learning new words, foreigners must get this distinction down right, it is key to having a decent accent in French, and in some cases avoiding misunderstandings. Yet when French roots were used in Esperanto, those vowels were leveled as just /o/ and /e/, respectively. That means that the learner does not learn the right French vowels from the start, and is likely to continue using in French the /o/ learned from Esperanto when the vowel is actually /ɔ/ etc. In modern language teaching, it is considered vital to avoid pronunciation mistakes from the very start, because otherwise they become too firmly rooted to get rid of later.