Leibniz is one of my heroes. I feel a special affinity to him. Most people are interested in his complex philosophical system. I find his metaphysical concepts very interesting too but I am also interested in the human story of Leibniz.
He was a polymath in the true sense of the word. He made important contributions to the fields of metaphysics, epistemology, logic, philosophy of religion, as well as mathematics, physics, geology, jurisprudence, and history. He was a philosopher, mathematician, physicist, historian, librarian, philologist, diplomat, lawyer, moralist, and a courtier. I cannot do justice to his intellectual legacy in a short essay. I will refer you to some books and resources on the web      .
One of the strangest things about him is that he preferred to explain his ideas in letters written to the leading intellectuals of Europe instead of publishing books. He only published one book in his lifetime, Theodicy. His other book titled Monadology was published posthumously. He wrote articles in some journals too but in comparison to the letters the 2 books and several journal articles constitute only a small fraction of his work. He wrote Monadology at the age of 70 just before he died. In Monadology he tried to give a summary of his philosophical system.
He wrote more than ten thousand letters. The exact number is not known. Leibniz exchanged letters with over 1100 different people in the course of his life. Those letters are still being collected, translated, interpreted and placed in proper context centuries after his death.
Although he devised one of the most complex and comprehensive philosophical systems in the history of mankind he never put it together in a systematic way in a book. The two books Theodicy and Monadology do not represent the full scope of his contributions. All other works were prepared for publication many years after his death. He once said that “One who knows me only by published works does not know me at all”.
Even though he was well respected during his lifetime the philosophers of his time did not think that he had a philosophical system because they never saw the full spectrum of ideas in one place. His ideas were scattered in letters.
Philosophers always attack other philosophers. I never understood that. The reason is ego, of course. I cannot forgive Voltaire for ridiculing Leibniz for his optimism. The “Candide”, Voltaire’s satire on Leibniz’s philosophy of optimistic determinism was very influential. Leibniz never saw this; the “Candide” was written in 1759, Leibniz died in 1716. Leibniz’s reputation was seriously damaged because of Voltaire.
Leibniz’s reputation fully recovered, of course, so much so that a prize was established in his name by the German government. The annual Leibniz Prize is given to 10 scientists working in Germany every year. Leibniz prize almost guarantees that Germany will be at the forefront of science for many years to come. At this rate all worthy German scientists will receive a large grant some time in their career.
Leibniz is known as one of the Rationalist philosophers along with Spinoza and Descartes. When the scientific method emerged and the Empiricism gained popularity the Rationalists fell out of favor. To our modern sensibilities the Rationalist approach seems quixotic. I find it incredibly naive that in the 17’th and 18’th centuries ambitious intellectuals believed that they could explain everything in the Cosmos by rational thought only. Descartes, Spinoza and Leibniz were convinced that human reason had the capacity to discover the true nature of Reality. I believe Kant named his famous book “The Critique of Pure Reason” to critique the Rationalists.
Today some of us have more nuanced views. I say we should let the scientists alone to discover the infinite perspectives of Reality while we try to identify with the source of Reality by transcending our egos. Some of us intuitively know that the mental realm is vast but still finite and there is a spiritual realm beyond the mental realm. Without gaining freedom from the confinement of the mind it is impossible to penetrate into the true nature of Reality. The “reason” is part of the mind. The “reason” is part of the mental realm.
Leibniz was a workaholic. He had tremendous energy. He preferred to work at night. His quick temper and irritability was probably due to the lack of sleep. He was a social person. He enjoyed conversations with people. He had many friends all over Europe. He could not be a diplomat without his social skills. Given his social nature, it is surprising that he never married. Like Newton he remained a lifelong bachelor.
He was bald hence the enormous black wig. He was always wearing his huge black wig of the type popular in the Paris of his youth. The wig and his old fashioned clothes became a subject of ridicule in his later years.
There is an episode from his younger years that I find very funny. Let’s read it from Roger Ariew’s account : “Leibniz went to Nuremberg to see some scholars who told him about a secret society of alchemists seeking the philosopher’s stone. Leibniz decided to profit from this opportunity and learn alchemy, but it was difficult to become initiated into its mysteries. He proceeded to read some alchemical books and put together the more obscure expressions – those he understood the least. He then composed a letter that was unintelligible to himself and addressed it to the director of the secret society, asking that he be admitted on the basis of his great knowledge, of which the letter was proof. According to the story no one doubted that the author of the letter was an adept alchemist or almost one; he was received with honor into the laboratory and was asked to take over the functions of secretary. He was even offered a pension.”
Apparently, he never took alchemy seriously. His rival Newton, on the other hand, was a life-long student of Alchemy which was never about turning lead into gold. The philosopher’s stone was not a stone. Alchemy is about Kundalini and the chakra system. Alchemy is very similar in this respect to the ancient practices of Tantra. Leibniz, probably, never understood this.
Speaking of Tantra, I also find it odd that Leibniz never mentions the Eastern Philosophy. He was a voracious reader. He was reading everything he could find. In his historian and librarian capacity he visited all the major libraries of Europe and devoured books. Leibniz studied Chinese history and philosophy . It is hard to believe that he never read about the Indian philosophy. There is no mention of the Middle-Eastern philosophers either. Middle-Eastern philosophers were the ones who translated the Greek philosophers, especially Plato and Aristotle. Leibniz grew up with the teachings of Aristotle. His mature philosophy shows influences from Plato and Neo-Platonism. He should have acknowledged the carriers of that knowledge. I think that his Lutheran Christian beliefs biased him against the Eastern Philosophy.
Physicists usually mention the controversy regarding the invention of differential calculus. I won’t go into that. It is now well established that he developed differential calculus independently of Newton. This contribution alone would secure his place in history but he contributed much more.
He was a genius, a polymath, and he was human. Fame is a funny thing. He was a child prodigy. In his 20′s he was recognized as a genius. In his 30′s and 40′s he was a bright star, yet only few people attended his funeral when he died in 1716 at the age of 70. Even though Leibniz was a life member of the Royal Society and the Berlin Academy of Sciences, neither organization honored his passing. His grave went unmarked for more than 50 years.
All ideas come from the Cosmic Mind. When we open our hearts and minds to divine inspiration we discover the same universal principles independently. Leibniz discovered many metaphysical principles. He discovered calculus independently of Newton. He thought he was the original thinker of these metaphysical principles but obviously ideas very similar to his were discovered by ancient sages. They did not write books or papers but they had similar concepts. It is not necessary for the philosopher to explain all the influences. Philosopher’s job is to build rational systems of thought or metaphysical models. The philosopher should realize, however, that there is nothing new under the sun. Philosophers re-invent the wheel all the time. That’s all right; there is nothing wrong with that.
I would like to conclude this essay by giving you a concrete example of how people discover things independently. For example, I noticed in 2008 that the Chinese “I Ching” hexagrams are a representation of the Q8 group in mathematics and I wrote an article  about it. Leibniz observed the same fact many centuries before; he said the hexagrams correspond to the binary numbers from 0 to 111111. When I wrote that article I had no idea that Leibniz observed the same fact before.
 “The Cambridge Companion to Leibniz”, edited by Nicholas Jolley, ISBN 0-521-36769-7
 “The Courtier and the Heretic”, Matthew Stewart, ISBN 0-393-05898-0
 “G.W. Leibniz’s Monadology: An Edition for Students”, Nicholas Rescher, ISBN 978-0415072847
 “Discourse on Metaphysics and other Essays”, ISBN 978-0872201323
 “The Rationalists: Descartes: Discourse on Method & Meditations; Spinoza: Ethics; Leibniz: Monadology and Discourse on Metaphysics”, ISBN 978-0385095402
 “Quaternion Group Q8 and Yi Jing (I Ching) Hexagrams”, http://sureshemre.wordpress.com/2011/12/31/quaternion-group-q8-and-yi-jing-i-ching-hexagrams/