(Avot 6:6) There are 48 ways to acquire Torah, including...binat halev, understanding...
(Genesis 11:7) ...v'ek'kha pat lechem v'sa'adu libkhem... (Abraham shows his divine visitors hospitality and offers ) ...let me fetch a bit of bread so that you may refresh yourselves...
The word "heart" appears in both of these texts, though an accurate translation nonetheless omits the word in both cases. The heart is a peculiar organ, but not for its medical function, which is clearly essential. Rather, it has a folk function as being the center of human being (that is, as the center of any one person's existence). I think you can tell what a society most values by what the culture attributes as the primary resident of the heart.
In America, it is obviously love. Though we are months away from Valentine's Day (and month's beyond its Jewish parallel, Tu B'Av), the universal symbol of the heart has become synonymous with love. And what we mean by love is commonly understood as a form of desire. (Hence, the English idiom "my heart's desire," that which the source of my love itself loves.)
Arguably, in medieval Europe, the heart was the locus of purity or evil, moral qualities that determined the character of the individual. Other characteristics turn up in the heart as well: bravery, determination, and pride, to name a few.
In the Bible and through the Rabbinic period, the heart was considered to have the functions of what we now know to be the brain. Knowledge, skill and most emotion were co-located in the human heart. (Favor was associated with the eyes, anger with the nose and indignation with the kidneys.) Like the brain, the heart was presumed to have two interconnected parts with separate roles. The right chamber of the heart contained the inclination to goodness, and the left chamber the inclination to wickedness. All of human activity resulted from the admixture and conflicts between these two impulses.
Our sages read the Bible very closely. Especially the disciples of Rabbi Akiva believed that nothing was superfluous in the Torah; every letter had a reason to be present and a meaning to be understood. So it did not escape notice that sometimes the word for heart was levav and sometimes it was lev. The doubling of the letter vet seemed ripe for interpretation, and indeed one of its most prominent examples-– in the first paragraph of the Sh'ma: b'khol l'vav'kha, with all your heart – is understood to mean that we must love God with both our inclination to goodness and our inclination to wickedness.
But Abraham's visitors, messengers from God, are understood to be angels. Angels, being mostly divine, are not afflicted with free choice. They can make no moral judgments and therefore have a heart with only one chamber, filled with the good impulse to fulfill the mission for which they were created. In our Torah verse, Abraham says, "v'sa'adu libkhem," literally, "feast yourheart." Here, the word has only one vet.
The wisdom contained in Torah address both sides of our natures. Goodness, or perhaps more accurately altruism, is everyone's goal. Wickedness, or perhaps more accurately selfishness, is everyone's obstacle to that goal. Torah offers us plenty of "thou shalts" to allow for the expression of the giving impulse, and even more "thou shalt nots" as a control over the urgency of the taking impulse.
But the one who seeks to acquire Torah cannot bifurcate its lessons. The love of God is accomplished b'hol l'vav'kha, with allyour heart, meaning both chambers. Love is generated from within the individual person, and we are by nature divided and conflicted. The teaching of God is indivisible. There are not one set of "dos" and one set of "don'ts," one set of rituals and one set of ethics, orone set of universal ideals and one set of particular practices. Acquiring Torah means seeking understanding as unified as an angel's heart.
I wouldn't want to be an angel; even those who are a permanentpart of the divine entourage gain direct knowledge of God at the expense of the glorious challenges of human potential and limitation. But I admire the ability of the angel to be single-hearted when it comes to God's wisdom, knowing that love and hate, Jew and non-Jew, old and young, yesterday and tomorrow are not so much opposites as they are complements. Binat halev, that single-hearted understanding, keeps us true to the one-ness of God by not tempting us to divide the divine nature into segments.
Try this exercise: Hold in your thoughts someone or something you alternately like and dislike. (In my case, it might be the Chicago Cubs.) Try to identify what causes your attitude to change back and forth. How do those causes fit into the whole of your subject of contemplation? Can accepting the wholeness of the person or thing mitigate your fluctuating emotions?