Although most people focus on the practice of meditation, morality plays an important role in the training leading to Enlightenment. It encompasses three elements of the Eightfold Path of Buddhism: Right Speech, Right Conduct, and Right Livelihood.  

It is not difficult to see the importance. Since it is impossible to achieve the peace of mind necessary for Enlightenment if you feel remorse or hold ill will.

Moral values are not simply socially relative or subjective concepts but originate from principles mandated by reason.  

Emmanuel Kant, in the Critique of Practical Reason, explains that the Moral Law is categorical (universal) and imperative (mandatory). It is a categorical imperative that “holds for everyone who has reason and will.”   

The human will is generally moved by desires of the ego. We employ practical reason to obtain what we want. Happiness is generally considered the satisfaction of cravings.

Moral Law originates from pure practical reason. It means that the awareness of right and wrong is independent of desires, is a priori. The Moral Law transcends mundane desires because pure practical reason is unconditioned:  

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, you are aware of the truth even if you choose to lie. The awareness of the decision is your free will. The Moral Law consists of absolute rules. This in contrasts to relative social rules dictated by cultural or religious norms.  

Because this transcendental Law is an imperative (a demand) of reason, it creates distress if ignored. This is what we call our 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 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 succinctly 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).  

This principle is a philosophical formulation of a complex idea. But generally, it argues for the existence, and human awareness, of universal goodness. As free-willed beings we can choose to ignore this reality or live by its moral principles. Human happiness, however, is only possible with the later.

By practicing morality, along with meditation, the mind becomes peaceful and content, making Enlightenment possible. 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…

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.