Coming from an academic background, I had a predisposition to make philosophy a dangerous thing, as I believe many of us do.  I enjoyed trying to tease the great truths from powerful spiritual writings.  Having some mental grasp of those truths, I felt myself to be more "spiritual," though in fact nothing about my life had actually changed; I simply had another piece of information in my mental library.  Believing I was more evolved simply for knowing, I actually missed much of the transformative power of the great works of yoga.  

Purna Yoga has one central premise when working with philosophy:

Knowledge is useless until applied.

What you know is not important; only what you live has relevance.  Purna Yoga focuses on incorporating the essential life lessons of the great works of spiritual philosophy into day-to-day existence:  the Vedas' four aims of life (finding purpose, creating abundance, cultivating pleasure and joy, and spiritual evolution), the Bhagavad Gita's emphasis on living your purpose (dharma), the Yoga Sutra's use of mental discrimination to understand the relationship between spirituality and the world, and the Hatha Yoga Pradipika's use of the body as a tool for spiritual progress.

Purna Yoga's life-centric take on philosophy reaches its apex with the work of Sri Aurobindo and his spiritual collaborator, the Mother of Sri Aurobindo Ashram, which forms the spiritual basis of Purna Yoga.  Sri Aurobindo stated it simply and elegantly:

All life is yoga.

Everything you do, say, think and feel is an opportunity to move closer to oneness with the truth of your spirit.  Yoga is not separate from life; life is not separate from yoga.  Transformation is what we seek, not information.

It is in each and every movement of the daily life that the Truth must be found and practiced.
— The Mother of Sri Aurobindo ashram

Applying philosophy in Purna Yoga -- an example:

As part of a Purna Yoga training, I did a "21-Day Experiment" in which I incorporated the concept of ahimsa (non-violence) into my life.   (21 days is considered a minimum to engrain a new pattern into the nervous system.)  Day 1 was pretty easy: I didn't hit anybody!  Then I went a layer deeper, and began to notice inconsiderate actions that created more of a subtle injury -- interrupting another person, driving aggressively, sarcastic humour, etc.  I began to see how leaving things untidy or disorganized disrupted the energetic flow of a room in an abrasive way.  As the experiment continued, I noticed the underlying violence in my "bargain" mentality -- I often chose cheap commodities whose production harmed the environment.  It was extremely sobering to watch my thoughts with the understanding that every unkind thought I have ever had left its ugly trace in the collective consciousness, because we are all connected.  By the end of the 21 days, I understood that, by virtue of this connection, any time I look at anyone as separate or different from myself, I have essentially committed an act of violence.  That realization has made me more understanding, open-minded, empathetic and kind.  I love more and better.  That is a powerful real-world shift with immediate and tangible benefits, and it can only happen from living a truth, not just knowing it.