Why do many words have silent letters when even without them the word would sound the same, like ‘island’ and many others.

Question

I tried asking my English teacher back in school but even she did not have an answer.

In: 157

Answer 1

Some letters were added in English in an attempt to bring the spelling closer to Latin, which was the language of educated people. Because of this S was inserted in “island”, and B was added to “debt”.