there's no such thing as a straight line

when i was really young, i showed my dad a drawing i had done using a ruler. he said, "nikki, there is no such thing as a straight line. you put a bunch of small lines together to make a line look straight." later a teacher in college told me there are nothing but straight lines and you put them together to make a curved line. both statement mean the exact same thing to me about a basic line drawing technique but i prefer the way my dad said it.