[Grammar] unless you have washed

[Oceanlike]

Is there any difference between the two sentences when simple past (washed) and present perfect (have washed) are used? What is the difference?

a) Do not start eating unless you washed your hands first.

b) Do not start eating unless you have washed your hands first.

Thank you.

 

[Yankee]

As usual context is a consideration, but let me start by suggesting that by using the condition "unless", the term "first" is unnecessary and actually redundant. With regard to your question, i.e. difference between a) and b), first, either would be understood in an immediate circumstance as requiring hands to be washed. But a) is a more immediate requirement, whereas b) could/would be used as a general rule and stated at any time past and prior to eating.

 

[GoesStation]

In general, sentence B is natural. To me, sentence A is not. Some Americans would use sentence A with no difference in meaning.

 

[jutfrank]

Sentence b) is correct, natural, and appropriate.

I cannot see how sentence a) could be preferable in any way, so I would say that it is not correct standard English, despite what some people may say.

 

[Yankee]

"Correct standard English" is most often in the ears of the listener. But I think we should ask the mothers of the English-speaking world about the use of a), with or without "first".

 

[jutfrank]

"Correct standard English" is most often in the ears of the listener. But I think we should ask the mothers of the English-speaking world about the use of a), with or without "first".

Yes, I now think I was wrong to suggest that sentence a) is not correct standard English. It does, as you say, depend on context (as always).

However, I do think that sentence b) is more likely. If we understand the situation to be a mother addressing her children at the dinner table, sentence b) works very well to provide an ideal context by which to illustrate how the present perfect can be used to provide present relevance to what's being said. Sentence a) doesn't do that. This was the pedagogical goal that I was aiming for in post #4. I assumed that Oceanlike was really wondering about the use of present perfect in utterances like this, in contrast to the past simple. I also assumed that sentence b) had been written as a model sentence for some kind of English language learning material, from which Oceanlike had then constructed sentence a) in order to explore the differences.

Of course I may be completely wrong about all this.

Oceanlike—please tell us: where did you find these sentences?

 

[Tarheel]

Say:

Do not eat until after you wash your hands.

Now let's get mom's input.

Mom: Wash your hands!
Little Betty: Okay, Mom!

;-)

 

[J&K Tutoring]

Your original post asked specifically for a preference between A. and B. You have received good responses on that question, so I'll expand a bit (Tarheel is on the right track).

For giving instructions- especially public notice- it's best to go with a positive statement. Don't tell people what not to do. There can be a hundred things to not do! Better to tell them the one thing they should do, as in:

Please wash hands before eating. OR

Employees must wash hands before eating.

 

[jutfrank]

Your original post asked specifically for a preference between A. and B.

It didn't. It asked for an explanation of the difference between present perfect and past simple in the context of sentences a) and b).

It didn't occur to me that this could be about a public notice. I see what you mean, though—the uncontracted use of Do not is not something that a mother at the dinner table is likely to say. But what kind of public notice would tell people to wash their hands before eating? Do you mean for schoolchildren, perhaps?

 

[J&K Tutoring]

It didn't. It asked for an explanation of the difference between present perfect and past simple in the context of sentences a) and b).

It didn't occur to me that this could be about a public notice. I see what you mean, though—the uncontracted use of Do not is not something that a mother at the dinner table is likely to say. But what kind of public notice would tell people to wash their hands before eating? Do you mean for schoolchildren, perhaps?

Of course jutfrank is correct in that the OP did not ask for a preference, and my use of the word specifically was a poor one. Most of the responses (including jutfrank's "I cannot see how sentence a) could be preferable in any way...") were in that direction, however.

My response about public notices- whether about washing hands (where I come from, many restaurants will have just such a notice in restrooms reminding employees to wash before returning to work), wearing a hardhat, staying in the left lane, or whatever- is that it's always best to keep things simple and concentrate on the positive, rather than telling people what not to do.
​

 

[Oceanlike]

Oceanlike—please tell us: where did you find these sentences?

I was doing grammar exercises. There are choices between 'washed' and 'have washed'.

 

[jutfrank]

I was doing grammar exercises. There are choices between 'washed' and 'have washed'.

So what is the correct answer? I'm guessing it's have washed.

 

[Oceanlike]

So what is the correct answer? I'm guessing it's have washed.

Yes, it was given as "have washed". I didn't understand why.

 

[J&K Tutoring]

Is there any difference between the two sentences when simple past (washed) and present perfect (have washed) are used? What is the difference?

a) Do not start eating unless you washed your hands first.

b) Do not start eating unless you have washed your hands first.

Thank you.

A. Would be preferred as a general statement for every eating situation if washed were changed to wash: Do not start eating unless you wash your hands first. Notice how both verbs are in the simple present tense.
B. This one refers more directly to a current situation- present or future- though it still stands as a general rule.

They both are a bit awkward. Better to simplify with: Wash your hands before eating.