In a written text, or even on a spoken thread of reasoning, if one uses the expression "on the other hand", is it mandatory that the expression "on the one hand" had previously been used?
I mean, could one say for example:
"I think that English grammar is such a difficult subject because there are so many exceptions to memorize, the so subtle use of prepositions and so one. See for instance the recently grammarian's discussions whether modal verbs are tenseless or not - I really prefer math. On the other hand, the inflection of verbs in that language is very easy compared to French or Spanish for example."
That is: Can one use 'on the other hand' without a previous 'on one hand' ?
PS Feel free to correct any mistakes in this post