Before I begin to explain my ideas on the importance of the Mental Universe I must make two qualifying statements.
First, to assume that the entire nature of the Universe, or maybe better said "Our Universe", is mental is not to negate the fact that there exists an objective Universe. That is, matter which exists outside human consciousness. I can be sure that our nearest neighbouring galaxy Andromeda long existed before it's known existence. What it undeniable is that matter exists outside consciousness. However, without consciousness matter has the same relative value whether it exists or not. A flower has no meed of the sun for its photosynthetic metabolism if the flower doesn't exist. Therefore, the ability to perceive matter is essential for its existence. As long as there is any type of living animal, vegetable, bacteria, archea or virus that exists within the Universe then we can assure ourselves that the universe exists. One could extrapolate upon this idea and argue that in the realm of the Multiverse there is surely one universe where its physical parameters do not allow for life. That being conceded I would like to re-emphasise that when I talk of The Mental Universe I am refering to our Mental Universe.
Secondly, the Mental Universe isn't just a concept that speaks of minds as we think of our own. The human brain is the most complex mechanism in the Universe and is the seat of what we think of as mind. This does not eliminate other types of life which can contribute to the Mental Universe. The Universe existed long before humantiy and will most likely continue to exist after our demise. What is becoming more evident with modern science is the fact that our Universe is very likely teeming with numerous forms of life throughout. The latest observations of exo planets have supplied us with the notion that unlimited possibilities exist for life in our Universe beyond our planet. Thus, to believe that life in its infinite possible manifestations has and will continue to accompany the existence of the Universe is more than most likely. There is the problem of the very birth of our Universe allowing no such conditions for any type of life. To understand that for 500 000 years after the Big Bang the Universe was completely black as it took that amount of time for the photon to exist permits is to rationalise the time scale on which the Universe was formed. Life has not existed since the very beginning of time as nor has light as nor any elements heavier than hydrogen and helium which took hundreds of millions of years to form in nuclear reactions and supernovae of stars. Thus the construction of our Universe is somewhat akin to that of Rome: it was not built in one day.