Dilgo Khyentse Rinpoche, one of the great Tibetan masters of the twentieth century, talks about the Buddhist concept of emptiness:
When a rainbow appears vividly in the sky, you can see its beautiful colors, yet you could not wear it as clothing, or put it on as an ornament. It arises through the conjunction of various factors, but there is nothing about it that can be grasped. Likewise, thoughts that arise in the mind have no tangible existence or intrinsic solidity. There is no logical reason why thoughts, which have no substance, should have so much power over you, nor is there any reason why you should become their slave.
The endless succession of past, present, and future thoughts leads us to believe that there is something inherently and consistently present, and we call it "mind." But actually... past thoughts are as dead as a corpse. Future thoughts have not yet arisen. So how could these two, which do not exist, be part of an entity which inherently exists?
However, that void nature of mind is not just a blank emptiness like empty space. There is an immediate awareness present. This clarity of mind is like the sun, illuminating the landscape and allowing you to see mountain, path, and precipice—where to go, and where not to go.
Although the mind does have this inherent awareness, to say there is "a mind" is to give a label to something that does not exist—to assume the existence of something that is no more than a name given to a succession of events. One hundred and eight beads strung together, for example, can be called a rosary, but that ‘rosary' is not a thing that exists inherently on its own. If the string breaks, where did the rosary go?
Dilgo Khyentse Rinpoche, The Heart of Compassion