Why does `if [false]` evaluate to true but `if false` doesn't in bash?

Running this script in bash will print "hello"

if [ false ]; then
    echo hello
fi

Running this script in bash will print "hello"

if [[ false ]]; then
    echo hello
fi

Only when I take away the brackets, bash will not print "hello"

if false; then
    echo hello
fi

I thought the entire premise of the brackets was to enable additional functionality like && and ||, why is it being counter-productive in this case?

edit: is this what you mean by bash quoting? still prints "hello"

test=false
if [[ "$test" ]]; then
    echo hello
fi

Solution

if function_or_program; then
    # do something
fi

This checks if function_or_program exits with 0 and if it does, executes the do something block.

true and false are functions (and programs) that exit with 0 and 1 respectively.
[ is a function (and a program, linked to test) that can be used to test strings and numbers.
[[ is a function that is similar to [ but is more robust.

So, what you observed is that when using [ and [[ you are testing the strings true and false. All strings that do not have the length 0 are considered true so both true and false will be seen as true.

I thought the entire premise of the brackets was to enable additional functionality like && and ||,

You can execute multiple programs/functions too:

if false || true; then
    # do something
fi

... and combining executing programs/functions with testing strings is also possible:

if ( false || true ) && [[ "$foo" == "$bar" ]]; then
    # do something
fi