All this, the positive and physical essence of mechanics, which makes its chief and highest interest for a student of nature, is in existing treatises completely buried and concealed beneath a mass of technical considerations.
It is easy to love friends and sweethearts. This is selfish love. Higher love embraces enemies and all ugly, bad people. The highest love doesn't see goodness or badness at all. One should even love warmongers, bad food producers and priests.