There is, it would appear, a downside to language. Language is invaluable for sharing knowledge and experience -- without it human culture would never have arisen. And thinking to ourselves in words can be very useful when we need to focus our attention, analyze a situation or make plans. But much of the remainder of our thinking is totally unnecessary. When I observe my own mind, I reckon that ninety per cent of my thinking I would better off without.
If half my attention is taken up with the voice in my head, that half is not available for noticing other things. I don't notice what is going on around me. I don't hear the sounds of birds, the wind, or creaking trees. I don't notice my emotions, or how my body feels. I am, in effect, only half conscious.
Just because we have the gift of being able to think in words does not mean that we have to do it all the time. This is something many spiritual teachings seem to have recognized. Most have techniques of meditation or prayer designed to quieten the voice in the head, and so still the mind. This is what the Indian word samadhi literally means, "a still mind" .
When the mind is still it is able to be more in the present, and more at peace. It is the natural state of mind that is our evolutionary inheritance. It is the state of grace to which we long to return; from which we fell when language took over our consciousness.
Moreover, say the sages, when the mind is completely still then we know our true identity. We know that we are at our core that faculty of consciousness that illuminates all beings. As the Chandogya Upanishad declared some three thousand years ago, "That which is the essence of all things, That art Thou."