Hi! So, I’ve just found out that qualify also mean ‘‘to limit, modify, or restrict’’, and that you have to understand how the author qualifies an argument. I don’t think I get it… From what I understand, to qualify an argument means to give extra information about the subject so that the argument doesn’t seem so emphatic. Can someone help me please?
For example, in AP Lang I was taught about “support, refute, or qualify.” When given a prompt that asks you to take a stance and defend it, you have three options.
Prompt: Should America declare war on ISIS?
Support: Yes, America should declare war on ISIS.
Refute: No, America should not declare war on ISIS.
Qualify: America should wait until we are provoked to make a decision about ISIS.
In this instance, “qualify” modifies the more extreme points of view to find a “maybe” answer.
Another example includes so-called “qualifying words” like sometimes, maybe, perhaps, may, etc. “People are always dumb” is a very black-and-white statement. But if you wanted to LIMIT that, you might say, “People can be dumb sometimes.”
Thanks @bogdangles, now I think I get it. 
On SAT 1, “qualify” is often used to show nuance. If “qualified [noun]” appears in an answer choice, look for a balanced or nuanced opinion:
The event was a success, although a few participants complained about overcrowding.
Antibiotics have been a triumph. They have saved countless lives. Yet they have also led to the emergence of a new class of anti-biotic-resistant diseases.
Professor Murphy is hard working, well prepared, and erudite, but he’s a pompous jerk.
Thanks @marvin100!