on one hand

Usage notes
This form of the idiomatic expression is not even mentioned in many dictionaries and is specifically proscribed in others (e.g. Longman Dictionary of Contemporary English). This is perhaps because leaving out the definite article could often be misunderstood, at least for a moment, as reference to a physical hand instead of the idiomatic use. The listener or reader however often quickly realizes that this wouldn't be logical or is already aware that an abstract situation is being described, as in this example: There was a conflict between their rationally held views on the one hand and their emotions and desires on the other.