The purpose of meditating on the dangers of lower rebirth is to generate a great fear of engaging in negative actions, the karmic cause of lower rebirth.  The perfection of fear of lower rebirth is we fear taking lower rebirth because if we do so we will become trapped in the lower realms for an incalculably long time during which all the being who we would otherwise have saved if he hadn’t fallen in the lower realms must continue to suffer.  The ultimate perfection of fear of lower rebirth is the perfection of the fear of lower rebirth conjoined by an understanding that our negative actions, the lower realms and all the beings who inhabit them are empty.

One of the biggest obstacles to our generating a fear of lower rebirth is we do not really believe they exist.  An understanding of emptiness provides us with a definitive reason proving their existence.  Many do not believe in lower rebirth because they do not believe in rebirth at all.  They believe that when the body dies, the mind dies with it and nothing remains afterwards.  They believe this because they believe the body creates the mind.  But in reality, it is the exact opposite – the body is merely a dream-like projection of the mind.  It is fairly straightforward to understand how the body is nothing more than a mere mental label imputed upon the parts of our body, and that if we took away all of the parts of our body there would be nothing remaining that could be considered our body.  The same is true of all of the individual parts of our body, they too are just mere mental labels imputed upon their parts.  While our ignorance assents to the body as being somehow real or solid, when we check carefully all we find is mental projection.  Death is no different than one dream ending.  The body of last night’s dream never was anything more than a mental creation and when we wake up we do not wonder where the dream body went – we understand clearly that it has simply dis-appeared.  But a new body appears in the waking world.  We have all had experiences of having dreams within a dream.  One dream ends and we wake up only to later find that we woke up into another dream.  When we wake up from that dream then we are back in this world.  In exactly the same way, our waking world is simply another layer of dream.  When the karma giving rise to the appearance of this dream body and dream world fully exhausts itself, the body of this life will dis-appear exactly as the body of last night’s dream did.

In any moment, the quality of the mind we have determines the quality of the karma that ripens.  If we have a negative mind, it functions to ripen negative karma giving rise to negative appearances.  If we have a positive mind, it functions to activate positive karma giving rise to positive appearances.  If we have a pure mind, it functions to activate pure karma giving rise to pure appearances. This process is happening all of the time – our every mind is functioning to activate certain karmic seeds and our every mental action in response to those appearances functions to plant new karmic seeds.  This process equally functions at the moment of our death.  The last mind we have at the time of our death determines the quality of our next rebirth.  Why?  Because if for example we have a negative mind at the time of our death it will activate a negative seed, but this seed will ripen in the first moment after our death determining the  karmic trajectory of our next life.  Just as when we are dreaming we believe everything to be real, so too when contaminated karma ripens it does so appearing to be real even though it is not.  Seen in this way, rebirth in the lower realms is no different than being trapped in a dream of being in hell from which we never wake up and which we do not realize it is a dream.

To take this one step further, it is very useful to ask the question:  who trapped all the beings in the lower realms?  If last night you dreamt of somebody in a wheelchair, who put them in it?  Clearly it was you, since it is occurring in your dream.  In exactly the same way, if you dream of countless beings trapped in the lower realms, who put them there?  Clearly it was you, since it is occurring in your karmic dream realm.  Every being is empty – another wave on the ocean of our mind.  When the ocean of our mind assumes the aspect of hell, all the beings of our dream become trapped there.  Our negative actions do not just condemn us to hell, but countless other beings as well.  Out of compassion, we therefore wish to never take rebirth in the lower realms!

Every time we engage in a negative mental action we create the causes for lower rebirth.  We engage in countless such actions every day.  Conversely, it is quite rare for us to engage in virtuous mental actions.  When we are in the lower realms, we engage in virtually only negative actions, thus creating countless causes to remain there.  When we take rebirth in the upper realms, we very quickly burn up all of our positive karma, leaving only negative karma on our mind.  We also almost never engage in purification practice.  Therefore, it perfectly stands to reason that we have countless trillions of negative karmic potentialities on our mind and very few, if any, positive ones remaining.  Every time we experience the slightest discomfort or problem, we usually respond by generating all sorts of negative minds towards our situation.  What can be more uncomfortable than death?  What can be a bigger problem than dying?  It is almost certain that we will respond with a negative mind at the time of death.  So with virtually only negative karma on our mind and a near certainty that we will respond to the death process with a negative mind, can there be any doubt about the fact that we are almost certain to fall in the lower realms at the time of our death?  This is not just something we say, this is the reality of our situation.  We are, for all practical purposes, on the precipice of hell and we can fall at any point.

If we deeply internalize this truth, we will generate a very healthy fear of negative mental actions and a very healthy fear of all of the negative karma which remains on our mind.  This fear will push us to cease generating negative minds and encourage us to engage in sincere purification.