The use of infinitives after certain verbs

In English, we sometimes get confused as to why certain verbs are in the present tense even after the earlier ones are in the past tense. The ones people misunderstand as verbs in the present tense are actually the infinitives. I can think of two verbs that suit this situation.

The first verb is 'recommend'. Look at the following sentences to see how infinitives are used after the verbs be they in the present or past tense.
1 I recommend that you see a doctor to diagnose your illness.
2 I recommend that he take up a driving course for his convenience.
3 She recommended that I go for a computer course.
4 She recommended that he seek a specialist for treatment.

If you look at the verb in Sentence 1 and 2, you will find that the verb is in the present tense. The infinitive in the first sentence is see while the infinitive in the second sentence is take. It is wrong to write 'I recommend that he takes up a driving course for his convenience.'

As for the third and fourth sentence, the verb is in the past tense, yet the infinitives are go and seek respectively. It is incorrect to say 'She recommended that he sought a specialist for treatment' or 'She recommended that he seeks a specialist for treatment.'

I shall now give another four examples of sentences using the verb suggest. The explanation is unnecessary as it is the same as the one for 'recommend'.
1 I suggest that you exercise regularly.
2 I suggest that he read more books.
3 She suggested that I join the same club as hers.
4 She suggested that he save some money every month for emergency use.

So much for infinitives used after certain verbs.