Is “Pick up those blocks” grammatically incorrect?

Question

I had someone correct me today as I instructed my child to "pick up those blocks." This person insisted that it should just be:

Pick up those.

since "those" is already plural.

Is this person correct?

Answer 1

The English demonstratives—this, that, these, and those—can all be used as either adjectives (“Those blocks are square”) or pronouns (“Those are square”).

Also, how would you distinguish “those blocks” from “those dolls” if you could only say “those”?

Answer 2

"Pick up those blocks" is perfectly correct. The fact that "those" is plural doesn't mean that you can leave out the object, "blocks." How would the child know what to pick up?

There's something off about the sentence "Pick up those," because the antecedent of "those" is missing.

"Should I pick up these or those?"
"Pick up those."

is OK. But by itself, it sounds wrong.

Answer 3

Removing the noun isn't a function of something being a plural. Your way is better.

Answer 4

It depends, actually, on the greater context. Two piles of blocks on the floor and my mother says to me 'pick up those blocks'. I start picking up one pile of blocks, but apparently it's the wrong pile because my mother says, 'no, pick up those'.

In the right context, it's fine, but only within a defining context. You can't make deixis work correctly without a shared referent.