  Apples, porcupines, and the most obscure Bob Dylan song---is every topic a
few clicks from Philosophy? Within Wikipedia, the surprising answer is yes:
nearly all paths lead to Philosophy. Wikipedia is the largest, most
meticulously indexed collection of human knowledge ever amassed. More than
information about a topic, Wikipedia is a web of naturally emerging
relationships. By following the first link in each article, we algorithmically
construct a directed network of all 4.7 million articles: Wikipedia's First
Link Network. Here, we study the English edition of Wikipedia's First Link
Network for insight into how the many articles on inventions, places, people,
objects, and events are related and organized.
  By traversing every path, we measure the accumulation of first links, path
lengths, groups of path-connected articles, and cycles. We also develop a new
method, traversal funnels, to measure the influence each article exerts in
shaping the network. Traversal funnels provides a new measure of influence for
directed networks without spill-over into cycles, in contrast to traditional
network centrality measures. Within Wikipedia's First Link Network, we find
scale-free distributions describe path length, accumulation, and influence. Far
from dispersed, first links disproportionately accumulate at a few
articles---flowing from specific to general and culminating around fundamental
notions such as Community, State, and Science. Philosophy directs more paths
than any other article by two orders of magnitude. We also observe a
gravitation towards topical articles such as Health Care and Fossil Fuel. These
findings enrich our view of the connections and structure of Wikipedia's ever
growing store of knowledge.
