Can present perfect and present simple be used in the same sentence?

Question

I occasionally say a sentence in which mixing the two tenses feels natural but in theory they express different relations to time so I am unsure whether this is correct.

One example sentence would be: 'I have found an article which reflects on this and I thought you may find it interesting.'

I think the 'I have found' part is correct since it doesn't matter when it happened and I am talking about why finding the article is relevant and not telling a story. But what about the 'I thought you may find it interesting' part? It feels more natural than saying 'I have thought you may find it interesting'. Is it because in that part of the sentence I am talking about the point in time when that thought came to me?

Thank you

Answer 1

It’s usually better style to use simpler forms when you can. Keep it short and sweet. There are some situations where the difference is important, though.

Take the example:

For more than a year, I wore a mask everywhere, but when I finally saw my parents again, they had gotten the vaccine.

This is a compound, complex sentence with three clauses: “wore a mask,” “saw my parents,” and “had gotten the vaccine.” None of the verbs can be in a different tense without changing the meaning.

The first clause has “wore a mask” because it describes what I constantly or consistently did during a period of time. If I had written, “For more than a year, I had worn a mask ..., but when I saw my parents,” that would mean that I finished wearing masks at the time I saw my parents, and was not wearing them afterward. (I might or might not have put one on sometime later.)

The second clause has “when I saw my parents” because it specifies a moment in time. When had my parents gotten the vaccine? By the time I saw them, that had already happened. If I had written, “but when I had seen my parents, they got the vaccine,” this would completely reverse the order of events: now, I’m saying I was already done seeing my parents when they got vaccinated. Saying “*when I had seen my parents, they had gotten vaccinated,” would be confusing. That just makes it unclear which happened first.

Finally, if I had written, “but when I saw my parents again, they got the vaccine,” that would mean that they got their vaccine while I was visiting them, rather than before.

Another example might be:

I had eaten lunch and was walking home when I heard a loud noise.

The order of events here is much clearer (At the moment I heard the noise, I had finished eating lunch and was in the process of walking home.) than if I had written, “I ate lunch and walked home when I heard a loud noise.” That could just as easily mean I heard the noise first, then ate lunch and finally walked home, or heard a noise, then walked home while eating lunch, or several other possibilities.

Answer 2

Yes, present perfect and the present can be combined in a sentence idiomatically and grammatically.

I feel very sick so I have scheduled an appointment with my doctor.

Now with respect to your example, the comments make sense.

I have found an article which reflects on this

is NOT grammatically wrong, but it is not particularly idiomatic. Most native speakers would use the simple past in this context

I found an article which reflects on this

But the idiomatic choice between simple past and present perfect is very dependent on context.

Over the last few days, I have found several articles which reflect on this

Now we are specifically talking about the recent past and perhaps multiple events that did not occur together. Here, at least my ear prefers the present perfect.

The fundamental difficulty with your example has nothing to with using different tenses in the same sentence. It has to do with using different tenses in a way that makes little or no sense.

I thought (then) it may interest you (now)

seems to imply that I no longer think it is of current interest to you. The words do not reflect your current thought.

I think (now) it may interest you (now).

Frequently, when something sounds odd it is because it distorts the intended thought rather than violating some grammatical rule.

I found an article which reflects this.

There no problem here with different tenses. You found the article in the past, but believe that the article reflects on the issue now.