Over the course of my life I have studied the teachings of every major religion and countless spiritual masters.  To this day, I remain firm in my belief that the message which has been communicated by these enlightened beings is universal and timeless. In the end, they have all spoken to one issue alone: TRUTH.
Naturally, the teachings have been expressed in different words and styles, depending on the time and culture in which they were delivered. But again, in the end, the TRUTH is simple, universal and timeless. To experience that infinity in every fiber of one's being is FULFILLMENT. To be out of touch with that infinity is emptiness.
Guru Nanak (1469-1539), not only preached about the universal truths; he also directly challenged the social, political and religious hypocrisy that ruled the day. In this regard, Guru Nanak's revolutionary Sikh movement in India ran very much parallel to the Protestant movement of Martin Luther (1483-1546) in Europe. 
Guru Nanak, through his sublime poetry, was able to brilliantly strip down religious thinking and practice to its barest essential: communion with God. On top of this, he showed us how to integrate God-consciousness into daily living and a just society. The simplicity and purity of his teachings remain absolutely relevant even as we enter this 21st century:

• There is but One God. By definition, this is the same God worshipped by all mankind, albeit in different ways and called by different names.
  
• God = Truth. (Sat Nam).
  
• God is experienced most directly through constant remembrance and absorption in His Name.
  
• The ultimate attainment of realization as a human being is that God and Me,  Me and God are One. This is pure ECSTASY. (Wahe Guru).
  
• The ideal spiritual life on this planet is to work by the sweat of your brow, share your earnings with    others and remember God's name through the busy hours of the day.
  
• Any form of caste system (division of society by predetermined class) is immoral and indefensible.
  
• Women are to be honored and treated as the equal of men. (This point of view was particularly revolutionary in Guru Nanak's day).
  
• A truly spiritual person does not retreat from the world. In fact, it is that person's responsibility to stand up against social and political injustice.