Buddha said:"What you are is what you have been, what you will be is what you do now."
Padmasambava also said:"If you want to know your past life, look into your present condition; if you want to know your future life, look at your present actions."
The Buddha taught that due to confusing our conceptions for ultimate reality we do not truly see the true nature of all phenomenon (dharma), and consequently all our actions of body, speech and mind will be based on ignorance. From acting or re-acting to our conceptions as if they were real arise feelings of attraction to pleasure, aversion to suffering, and more ignorance or delusion, which results in the laying of more deluded habitual imprints on the mind, and the consequentual deluded experiences, and so on, which we can term 'karma'.
So karma put simply is any action of mind motivated from ignorance of reality, or in other words any action of ,and caused by, our habitualy instinctive self grasping mind.
What does this mean for beings who have yet to realize the true nature of phenomenon or reality (dharma)? It means that through our karma, we are our own creators. And how we each experience life is individualy dependant on our individual karma. This beginningless cycle of karmic actions or re-actions based on ignorance of ultimate reality and the resultant lives and experiences (the missery of sufferings and temporary pleasures) is called Samsara.
Why is it beginningless? Because if the present moment of habitual mind comes directly from a previous similiar moment of habitual mind, ie action and reaction within the same mind continuum, then it follows there was no actual beginning, each moment of mind being separated by its own beginning and end which is the start of the next moment etc. since beginningless time. (see the medium scope for a deeper explaination)
The Buddha taught the four principles of Karma. (1) Actions produce similiar consequences, ie virtuous actions (kushla) produce pleasant results and non-virtuous (dashakushla) or harmful actions produce un-pleasant results. (2) The consequence is greater than the action. (3) There can be no consequence without the preceding action. (4) Karma dosen't just fade away but will ripen into a result when the right conditions or secondary causes are present, unless nullified by opposing karma, ie. non-virtuous actions can destroy virtous karma and virtous actions can destroy non-virtous karma.
So what are the non-virtous actions which bring much suffering? The Buddha listed ten main actions to be abandoned; Three of body, killing, stealing and sexual misconduct. Four of speech, false words, devisive speech, insulting words and idle or mindless gossip. Three of mind, covetousness, harmful intent and wrong view (of reality).
The Buddha taught three realms of samsaric beings, from lowest, (1) Desire, (2) Form and (3) Formless. These last two are smasaric pleasure or bliss realms, and all realms can further be divided. Through karma we can take re-birth into one of these realms, humans and animals etc are reborn into one of the Desire realms.
So while our actions come from karma, we will continue to cycle up and down through the three samsaric realms, experiencing moments of temporary pleasure and suffering dependant on our karmic reactions to the conditions we meet and the consequentual habits we reinforce or form.
As the Buddha said,"The three worlds are impermanent, like clouds of autumn. The births and deaths of beings are like watching a dance. The speed of human lives like lightening in the sky. It passes swiftly like a stream down a steep mountain."
NEXT... Ego in the Medium Scope