The man
Eckhart von Hochheim was born around 1260 in Thuringia, in what is now central Germany. He joined the Dominican order young and rose as high in it as a man could rise. He held the chair of theology at Paris twice, an honor that in his century puts him in the company of Thomas Aquinas, and he spent long stretches of his life as an administrator, running priories and a province, trusted with money and buildings and the training of preachers. He was not a hermit or an outsider. He was the establishment.
What made him dangerous came later, when he began preaching in German. Latin was the language of careful theology, fenced with qualifications that only the trained could read. Eckhart stood in front of nuns and townspeople and said the deepest things he knew in their own tongue, without the fences. The sermons that survive are the ones his listeners loved enough to copy by hand.
The Godhead behind God
His central move is easy to state and endless to absorb. The God we speak about is God in relation to creatures: creator, judge, father, the one addressed in prayer. Eckhart kept pointing past every relation to what he called the Godhead, the nameless ground out of which even the word God rises. Names describe relations, and the ground has none.
I pray God to rid me of God.
He meant that every concept of God, however holy, is still a concept, and the ground lies beneath all of them. And he paired it with a claim about us that is the real live wire in his preaching: the soul has a ground too, and in its depth the two grounds are not two. When the Upanishads say thou art that, they are making the same claim from another hill. Eckhart made it from a Christian pulpit, in the vernacular, to laypeople.
Subtraction
His method follows from his map. If the ground is already there, beneath the furniture of thought, then nothing needs to be acquired. What he preached was detachment, a releasing of everything the mind grips, images and desires and outcomes, until what was always underneath stands plain.
To be full of things is to be empty of God. To be empty of things is to be full of God.
If you have read the practice on the front page of this site, you have read Eckhart. Subtraction was his whole method. He did not teach climbing toward a distant God. He taught putting things down until the ground shows.
The trial
In 1326 the archbishop of Cologne opened heresy proceedings against him. It was an extraordinary step against a theologian of his rank, and Eckhart met it with a professor's answer: error belongs to the intellect and heresy to the will, so he might be shown wrong, but he could not be a heretic, because he submitted in advance to correction. He appealed to the pope and walked to Avignon to defend himself. He died there, most likely early in 1328, before any verdict reached him.
The next year a papal bull condemned a list of statements drawn from his work, some as heretical, some as rash. It did not work. The nuns and beguines who had heard him kept their copies. His students Tauler and Suso carried the teaching forward, and seven centuries later he is read more widely than ever, inside his church and far beyond it.
The same ground
This site keeps saying that the traditions are reports from different hills. Eckhart matters because his hill was Christian ground, and he did not import a word of his teaching from anywhere else. A Dominican professor, formed entirely by scripture and the schools, dug straight down through his own tradition and struck the same bedrock Vedanta calls Brahman, Lao Tzu left nameless, and Plotinus called the One. When the digging goes deep enough, the reports agree.
Where to begin
Start with the German sermons. The old translations are long out of copyright and free to read online, and the sermons are short, meant to be heard rather than studied. Read one slowly, the way you would listen to someone who means every word. He is difficult the way still water is difficult. Nothing is hidden, and that is the difficulty.