You are the ultimate authority on everything, whether you like it or not. It is us who decides which gurus are right and which wrong, and how much, and so on. It was always us. You are a light unto yourself whether you like it or not. That's the only light there ever is or ever was or ever will be. I believe that when all is said and done one finds oneself utterly alone.
We may be a flame that is hard to ignite without the rite conditions. A fire can much easier ignite if it has the rite wood and for instance birch bark and kindling to start it but without the rite ingredients it can lie dormant for years if not centuries. The guru provides the rite elements for me and many others that ignites the spiritual flame.
