Same is with the philosophical truth of God & this world. As per the scriptures, God created this universe & sit's in an invisible way in every nook & corner of the universe. This outer visible world is His creation, while He is there within this world in an invisible way. This whole world is changing all the time, while God is constant, changeless.
But why it is so, that we cling to this visible world only & just forget the invisible God, who is the creator of this world. It is due to our ignorance only. In philosophy, it is said that we are clinging to Maya (visible world) & ignoring the God who is the real thing. So that's why, it is said that we should not cling to the unreal, untruth (Maya) & should turn our mind towards the God, who is the only reality & truth. Just like alighting a small lamp eats away all the darkness in the room, so just by illumining your intellect with the knowledge, shall lead you to the truth of God.
Now, why do we fall in to ignorance? It is all due to the Nature born "TamoGun" (mode of ignorance) which we put into practice in our lives. "Tamas" or "Tamo Gunn" is the mode of Nature which is responsible for ignorance, delusion, indolence, laziness and sleep in a person. We should not fall a pray to this "TamoGun".
Here below is a story "The Lost Son" by Gautama Buddha who is teaching us through this story that we should not cling to the untruth, as when we fall a pray to the ignorance, then we do not see things clearly & ultimately it harms our life only.
"A young widower, who loved his five year old son very much, was away on business when bandits came who burned down the whole village and took his son away. When the man returned, he saw the ruins and panicked. He took the burnt corpse of an infant to be his son and cried uncontrollably. He organized a cremation ceremony, collected the ashes and put them in a beautiful little bag which he always kept with him.
Soon afterwards, his real son escaped from the bandits and found his way home. He arrived at his father's new cottage at midnight and knocked at the door. The father, still grieving asked: "Who is it?" The child answered, it is me papa, open the door!" But in his agitated state of mind, convinced his son was dead, the father thought that some young boy was making fun of him. He shouted: "Go away" and continued to cry. He shouted time & again, "Go away" "Go away". After some time, the child left.
Father and son never saw each other again."
After this story, the Buddha said: "Sometime, somewhere, you take something to be the truth. If you cling to it so much, even when the truth comes in person and knocks on your door, you will not open it."
Now here below is a verse from Bhagwat Gita which also tells us that in this whole creation, unreal has no existence, and the real (God) never ceases to be, So we should always turn our mind towards the God who is the only reality & truth.
"na-asato vidyate bhavo
nabhavo vidyate satah
ubhayor api drsto ’ntas
tv anayos tattva-darshibhih" (Bhagwat Gita: Chapter Two verse 16)
"Sri Krishna said: The unreal has no existence, and the real never ceases to be; the reality of both has thus been perceived by the seekers of the truth.