# Difference between: "This is as fast as it goes." VS "This is the fastest it can go."

An old lady who is riding on an stairlift to climb upstairs in her home says:

"This is as fast as it goes."

I think, she thinks the stairlift is very slow and it should go faster, but this is the way those stairlifts are designed.

[added in from OP's comment below]
We were taught at school that the structure "as +adjective + as " is used when you are comparing two things, and there is no comparison in this situation. For instance "This car is as fast as that car." There is a comparison and it makes sense. But, in the case of stairlift there is nothing else to compare its speed with. So, the structure of comparison did not seem to compare it to anything else. Maybe it is comparing it in itself.

But in such situations, shouldn't we say:

"This is the fastest it can go."

Why does she use the structure "A is as fast as B", which we use to compare things?

• She can say either. Both are correct. Oct 14, 2023 at 14:07
• Or #3: This is the fastest it goes. Or #4 This is as fast as it will go can go*. Or to reduce / eliminate the implied criticism of it not going faster, This is how fast it goes. Oct 14, 2023 at 15:58
• Why don't you think both versions are correct?
– gotube
Oct 14, 2023 at 18:02
• @gotube, because we were taught at school that the structure "as +adjective + as " is used when you are comparing two things, and there is no comparison in this situation. For instance "This car is as fast as that car." There is a comparison and it makes sense. But, in the case of stairlift there is nothing else to compare its speed with. So, the structure of comparison did not seem to compare it to anything else. Maybe it is comparing it in itself. So, I got confused and wanted to clear it. Oct 14, 2023 at 18:12
• @TimR, yes good explanation. I did not think "this" and "it" would be pointing to different things. I thought "this" and "it" both referred to the stairlift, but when you think about them sepereately, you get to understand why that structure is used. Oct 14, 2023 at 18:19