Mind is ever restless. Meditation aims at restraining the mind's wandering and ultimately steadying it. Conventionally this is sought to be achieved by total stoppage of thought But to stop the flow of thoughts for any length of time is extremely difficult, if not impossible. In fact, any attempt to suppress the mental activity makes the mind more restless than ever.
In Preksa meditation, however, the mind is engaged in concentrated perception on an object of a phenomenon. Here mental functioning is not stopped or suppressed, but regulated and channelized. In other words, the streams of thought flowing in different directions are channelized and made to flow in one direction.
Thus regulated and disciplined, mind can be made to concentrate in the perception of a single event or a phenomenon for a good length of time. The mind, thus engaged in the function of perception, is not available for that of thinking.