 Consider the proscription of ploughing with an ox and an ass yoked together. Does this imply a duty to base agriculture on animal power and to create the opportunity for fulfilling the prohibition? Reversing the terms, is mechanized agriculture, which obviates the use of animals as a source of energy forbidden because it removes all opportunity for observing this mitzvah? Or is it permissible to assume a hypothetical imperative: in the event that animals are used, avoid ploughing with an ox and an ass yoked together? (Judaism, 149)