needs to do his duty

[navi tasan]

1) He needs to do his duty, but he won't.
2) He needed to do his duty, but he didn't.

3) I need to clean the kitchen, but I won't.
4) I needed to clean the kitchen, but I didn't.

Are these sentences grammatically correct?

Are they logical?

Are they idiomatic?

 

[emsr2d2]

Are 2 and 4 supposed to be past tense versions of 1 and 3, with the change of tense being the only difference in meaning?

 

[navi tasan]

Thank you very much, emsr2d2,

Yes. I wanted to make sure that the sentences work both in the present tense and in the past tense. I hope there is no change in meaning.

 

[jutfrank]

The past tense of 'won't' is 'wouldn't,' not 'didn't'.

When you change tense, and especially when you change the tense of modal verbs, you necessarily change the meaning.

 

[Annabel Lee]

. . .
2) He needed to do his duty, but he didn't.
. . .
4) I needed to clean the kitchen, but I didn't.

. . . Are they logical?

Technically, the ellipsis after the auxiliary verb at the end of all four sentences could be interpreted in two ways, and with (2) and (4) one of the interpretations is a logical contradiction. Precisely because of this, however, no one would interpret it that way.

2a) He needed to do his duty, but he didn't [do his duty]. LOGICAL
2b) He needed to do his duty, but he didn't [need to do his duty]. ILLOGICAL

4a) I needed to clean the kitchen, but I didn't [clean the kitchen]. LOGICAL
4b) I needed to clean the kitchen, but I didn't [need to clean the kitchen]. ILLOGICAL