Although most people focus on the practice of meditation, morality plays an especially significant role in the training leading to Enlightenment. In fact, it encompasses three elements of the Eightfold Path of Buddhism, namely: Right Speech, Right Conduct, and Right Livelihood.
It is not exceedingly difficult to see the importance since it is impossible to achieve the peace of mind and detachment necessary for Enlightenment if you feel guilt or maintain immoral values or habits. But even more significantly, because moral values are not simply socially relative or subjective concepts but originate from principles mandated by reason.
Emmanuel Kant explains, in the Critique of Practical Reason, that the Moral Law is categorical (universal) and imperative (mandatory). The Moral Law is a categorical imperative because it “holds for everyone who has reason and will.”
The human will is generally moved by desire, by the demands of nature and by the idiosyncrasies of the ego. Happiness is then considered the satisfaction of desire. But the Buddha discovered that the primordial cause of suffering is desire: the desire for the things of the world which are intrinsically impermanent and can thus never satisfy the Self.
Moral Law, however, originates from pure practical reason which transcends empirical causation. It is therefore a priori and unconditioned. This simply means that the consciousness of right and wrong is independent of mundane desires. The Moral Law transcends mundane desires because pure practical reason is autonomous:
Thus freedom and an unconditional practical law reciprocally imply each other . . . It is therefore the moral law, of which we become directly conscious . . . that first presents itself to us, and leads directly to the concept of freedom. (Critique of Practical Reason)
For example, if you are faced with a decision of lying or telling the truth, you are conscious of that decision even if you choose to lie to obtain the object of your desire. The consciousness of the decision is your free will.
The Moral Law consists of absolute rules, which are independent of any object of desire or personal interest, such as: being truthful, not causing needless injury, respect for others. This in contrasts to relative social rules dictated by cultural or religious norms.
Now, because this transcendental law is an imperative (a demand), it creates stress and suffering if ignored. This is the emotional distress we call conscience.
Conversely, by obeying the urging of the Moral Law, that is, by living a virtuous life (with integrity, honesty, respect of others) one finds the freedom leading to a transcendent happiness that Kant identifies as contentment:
Freedom and the consciousness of it as a faculty of flowing the moral las with unyielding resolution is independence of inclinations, at least as motives determining (though not as affecting) our desire, and so far, as I am conscious of this freedom in following my moral maxims, it is the only source of an unaltered contentment. (Critique of Practical Reason).
Emmanuel Kant formulated the underlying principle of the Moral Law as:
Act only according to that maxim whereby you can at the same time will that it should become a universal law. (Categorical imperative – Wikipedia).
Which is a philosophical way of stating the Golden Rule: Do onto others as you would have done onto you.
By practicing Right Speech, Right Conduct, and Right Livelihood, along with meditation, the mind becomes peaceful and content, and thus avoiding the ill consequences of wrong actions (akusala-kamma), follows the path to Enlightenment. This the Buddha summarized this in his Meta Sutta:
. . . Let them be able and upright,
Straightforward and gentle in speech,
Humble and not conceited,
Contented and easily satisfied,
Unburdened with duties and frugal in their ways.
Peaceful and calm and wise and skillful,
Not proud or demanding in nature.
Let them not do the slightest thing
That the wise would later reprove . . .
May all beings be at ease!
Let none deceive another,
Or despise any being in any state.
Let none through anger or ill-will
Wish harm upon another.
Even as a mother protects with her life
Her child, her only child,
So with a boundless heart
Should one cherish all living beings . . .
Freed from hatred and ill-will . . .
One should sustain this recollection.
This is said to be the sublime abiding.
By not holding to fixed views,
The pure-hearted one, having clarity of vision,
Being freed from all sense desires,
Is not born again into this world.