Solomon sums up the effect on the human mind of the endless repeating cycles that he has described in the last few verses. To observe them and to think deeply about them is to be filled with weariness for, as we try to trace these endless patterns, the heart grows sick with the ceaseless futile activity of everything, and the unprofitability of it all.
This is about human appetites. If we try to grasp the world with our senses, and if you depend on it for happiness and turn to it as the ultimate source of satisfaction for the soul, you will be bitterly disappointed as you discover that you have taken vanity itself into your soul. Though life may be full of effort, the eye will never be satisfied with seeing. You will not be content for long. Things which engage your enthusiasm for a time will soon fail to excite us. The grass will always be greener on the other side. The ear will not for long be satisfied with the things it hears. This is not just because we are hard to please. It is because we all have built into us a deep sense that we ought to be alive in a spiritual way. Everyone has this instinct.
This verse confirms the idea that the subject is man’s appetite. All things go on in a circling and predictive manner. All of this is valuable to the preacher, to show the vanity of life and to silence the young mind which thinks that religion is predictable and dull and boring. No, it is life without God that is predictable and boring.