But if you are presenting a new proposition, it is necessary to

explain its nature, its workings, its principles and appliances
But if you are presenting a new proposition, it is necessary to
explain its nature, its workings, its principles and appliances. If
you are trying to sell a fountain pen you will not waste valuable
space in explaining to the reader what a fountain pen is good for
and why he should have one, but rather you will give the reasons for
buying your particular pen in preference to others. You will explain
the self-filling feature and the new patent which prevents its
leaking or clogging.