infinitive-to grammar

Question

I learned that I can not put -ing form after the infinitive-to; I should put base form of verb after the infinitive-to.

However, in this sentence, (this is from my textbook.)

They were able to dedicate all of their time to ensuring that I did well in school.

I can see ing form is used after infinitive to.

I am curious that why this sentence is grammatical even though it violates the constraint, and I want to know if I can change given sentence into They were able to dedicate all of their time to ensure that I did well in school.

Answer 1

Unfortunately in non-native English speaking countries, especially in India, even teachers teach wrong! I'm a victim!

infinite -to does not take -ing - plain wrong!

It's called a verb pattern. And, there are many verbs that take the -ing form after them. In fact, it's gerund.

The commonest is -

I'm looking forward to meeting you.

Interesting? Learn more on verb patterns here on Cambridge. Not just -ing, you'll learn more on that!

Another blog that answers it completely is here. It describes three possible rules on that.