Preface: I know that  'positive' means the acceptation in philosophy of ["dealing only with facts"](http://www.etymonline.com/index.php?allowed_in_frame=0&search=positive).

>[[Source: 80% down the page:]](https://courses.edx.org/courses/course-v1:UQx+META101x+3T2015/courseware/6e89b9518497427d8c4dffb8f0005a93/13d8e2107df147fb88245cac06a2aeb7/) Should we instead just decree that knowledge is justified true belief provided that, additionally, there is no element of luck involved? This is an odd suggestion for several reasons. First it would be odd to have a negative criterion in the definition of knowledge. There not being any luck involved is not some thing, that is, it’s an absence of a thing or a nothing. **A nothing or non-thing cannot be a cause of something positive.** What doesn't have any being as a thing cannot explain why someone knows something if knowing something is something positive.

Please assist me to understand the bold. How is this true, even for epistemology?

For example, suppose that I lack any knowledge of epistemology. Then this lack would cause and inspire me to read and learn about epistemology, after which I would have gained truly positive knowledge. So my example attests that absence of something can cause something positive?