You ought to obey the rules of the office,
indicates that it is your duty to obey because it is the right thing to do even though no penalty is attached.
You must obey the rules of the office,
indicates that you will be punished if you do not obey.
Those forms of the verb which express the time of the action are called tenses. No particular difficulty attends the use of the tenses except in the case of shall and will and should and would.
Shall and will are used as follows: In simple statements to express mere futurity, use shall in the first person, will in the second and third; to express volition, promise, purpose, determination, or action which the speaker means to control use will in the first person, shall in the second and third.
The following tables should be learned and practiced in a large variety of combinations.
| Futurity | Volition, etc. | |||
| I shall | We shall | I will | We will | |
| You will | You will | You shall | You shall | |
| He will | They will | He shall | They shall | |
A good example of the misuse of the words is found in the old story of the foreigner who fell into the water and cried out in terror and despair "I will drown, nobody shall help me."
In asking questions, for the first person always use shall, for the second and third use the auxiliary expected in the answer.