Initiatic Science teaches us that before reaching the bright and clear regions of the causal or higher mental plane, the disciple must cross through the murky regions of the astral and lower mental planes. These regions are like patches of fog and dust.
The fog is produced by excessive moisture of the heart: emotionality, sentimentality, greed and envy. As for the dust, it is produced by the practices and speculations of the intellect which only seeks out its own interests.
And dust, like fog, prevents us from seeing things clearly.
Not only does an initiatic teaching instruct humans about the existence of the different worlds, it provides them with the criteria to discern the quality of their states of consciousness, as well as methods for crossing through the zone of illusory perceptions to reach reality. By virtue of work and exercise, the day is coming when the psychic world will appear to them with the same clarity, the same sharp focus as the physical plane.