Four Species: Four Types Of People
Adapted from Likkutei Sichos, Vol. II, Simchas Torah; Vol. IV, Sukkos; Vol. XIX, Sukkos
The holidays celebrated in the month of Tishrei are of comprehensive significance  and the symbolism associated with their distinctive mitzvos is broad in scope.
In this context, the Midrash  explains that the mitzvah of the lulav and esrog symbolizes the intrinsic unity of the Jewish people. The fulfillment of this mitzvah requires us to hold together either fruit or branches from four different species of trees - the date palm (lulav), the myrtle (hadas), the willow (aravos), and the citron (esrog).
These four species are noticeably different from one another.
The esrog has both a pleasant taste and a pleasant fragrance. The fruit of the tree from which the lulav is taken, the date, has a pleasant taste, but no fragrance. The myrtle has a pleasant fragrance but no taste, and the willow has neither fragrance nor pleasant taste.
Taste symbolizes Torah study, because understanding Torah gives us a concrete pleasure, similar to the sensation of experiencing a pleasing flavor.
Smell symbolizes the fulfillment of mitzvos, because the quality which usually motivates us to fulfill the mitzvos is kabbalas ol, an unquestioning acceptance of the yoke of heaven.
Since we often do not understand the reasons for the mitzvos, their observance may be less tangibly gratifying than Torah study is, in much the same way that smelling something is less palpably gratifying than tasting it.
An extension of this symbolism enables us to see each of the four species as representing a different type of individuals.
The esrog represents a person who studies Torah and fulfills the mitzvos, the lulav represents one who studies Torah but does not perform mitzvos,  the myrtle represents one who fulfills mitzvos but does not study Torah, and the willow represents a Jew who neither studies Torah nor observes mitzvos.
Fulfillment Depends on
One's Connection with His Fellow Man
The mitzvah of the lulav and esrog demonstrates that no individual can attain fulfillment unless he is willing to go beyond himself and join together with his fellow man.
Even the esrog, the species which symbolizes both the virtues of Torah study and observance of the mitzvos, cannot be used for the mitzvah on Sukkos unless it is taken in hand and held together with the humble willow.
By the same token, no matter how much we develop ourselves as individuals, we cannot reach our true potential without the help of others. The unity of our people as a whole is an indispensable ingredient in the growth and progress of every individual.
The concept of unity is so central to this mitzvah that it is reflected not only in the requirement of taking all four species together, but also in the characteristics of the individual components of the mitzvah.
Our Sages  stipulate that a lulav may be used for the mitzvah only if its leaves are bound together.
The only species of myrtle that may be used for the mitzvah is that which has successive rows of three leaves each.
In each row, the three leaves must be level with each other, with no leaf significantly higher or lower than another.  The species of willow used also expresses the concept of unity, since it grows in bunches. 
Growing from Our Contact with Others
The motif of unity is also reflected in the esrog.
Indeed, because the esrog represents a category of people whose potential for achievement is greater than that of others, its emphasis on unity must be greater. 
The esrog expresses the concept of unity by virtue of the fact that it grows on the tree for an entire calendar year,  and is exposed to all the seasonal variations and changes of climate.
Not only does the esrog withstand all these influences, but it responds positively to them; each of these influences contributes to its growth.
We must learn from the esrog, and not merely tolerate people of all kinds, including those with characters and personalities very different from our own, but actually grow through contact with their divergent perspectives.
As the Mishnah  teaches, " Who is wise? - One who learns from every man."
Stages in a Sequence
These expressions of unity on Sukkos  are related to the motif of unity in the holidays that directly precede it, Rosh HaShanah and Yom Kippur.  There is, however, a difference between the approach to unity of Sukkos and that of the Days of Awe.
During the Days of Awe, our awareness of unity stems from the unique spiritual experiences of those days, during which we all step beyond our individual selves and establish contact with the fundamental G-dly spark in our souls.
At the level of soul where no separation exists between man and G-d, no difference exists between one man and another. On Rosh HaShanah and Yom Kippur we are thus able to pray together as a collective entity.
Despite the intensity of this experience, it has a drawback.
Since the feeling of unity we experience on the Days of Awe stems from a level in our souls far above that of our ordinary, everyday thought processes, after the holidays have passed and we return to the realm of ordinary experience, we may revert to a feeling of separation.
Sukkos teaches us that we must remain unified even at the level where a person's individual identity is taken into consideration, where one of us is an esrog and another, a willow.
Although differences may exist with regard to our potentials and the degree to which we have developed them, we still stand united, bound together in one collective entity. 
The sequence of the holidays is vital.
The all-pervasive experience of the Days of Awe and the essential awareness of unity that they evoke prepare us for the lesson of unity taught by Sukkos.
The intense spiritual service of the Days of Awe jolts us out of our self-consciousness and enables us to reorient our values, so that we can relate to each of our fellow men as we ought.
A Joyous Bond of Oneness
This progression towards deeper unity reaches its peak on Simchas Torah, when the scholarly and the unlettered, the observant and the non-observant, Jews from every background and way of life, join together in exuberant dancing with the Torah scrolls.
Personal differences that at other times would divide them, fade away.
This unity is given tangible expression by the custom of dancing on Simchas Torah in a circle.
A circle has no beginning and no end and every point is equidistant from the center.
On Simchas Torah we forget who is a "head" and who is a "tail".
A common nucleus unites us all and fuses us into a collective identity.
While Sukkos teaches us that even as individuals we stand together as a unified people, Simchas Torah takes us even further. At this time we lose all consciousness of our individual identities: we step completely beyond ourselves.
The experience of Simchas Torah is not, however, a return to the level of the Days of Awe, during which we transcend our individuality through a spiritual service, linking with others above the level of ordinary experience. For on Simchas Torah, the absolute bond of togetherness is revealed within ordinary material experience, in the midst of eating, drinking, and dancing.
These joyous bonds of unity will herald the coming of the time when "a great congregation will return here:"  we will return to Eretz Yisrael as one cohesive nation. At that time, as promised by the prophets, "they will be crowned by eternal joy."  May this take place in the immediate future.
- (Back to text) For the Hebrew letters of the word Tishrei can be
rearranged to form the word, reishis, meaning "head of"
(Baal HaTurim, commenting on Devarim 11:12). This implies
that just as the head controls the function of the entire
body, so too, does the month of Tishrei have an effect on
the entire year to come. [Regarding Rosh HaShanah as the
"head of the year," see the above essay entitled "At One
with the King"].
- (Back to text) Vayikra Rabbah 30:12.
- (Back to text) The Midrash obviously does not intend to imply that
people in this category do not perform mitzvos at all.
On the contrary, our Sages teach (end of Tractate
Chagigah) that even "the sinners of Israel are as full of
mitzvos as a pomegranate [is full of seeds]." The Midrash
is speaking here of scholars who focus their divine
service on excellence in Torah study and regard mitzvos
merely as media necessary to achieve that goal, but
otherwise without independent importance.
The same applies to the categories of Jews represented
by the willow and myrtle. There, too, the expressions
"without taste" and/or "without fragrance" are not
absolute, but imply that the area described is not the
area of primary focus.
After all, as quoted above, the very same Jew who is
likened to the willow is also likened to the pomegranate.
- (Back to text) Sukkah 32a.
- (Back to text) Ibid. 32b.
- (Back to text) Shabbos 20a. See also the series of discourses entitled
VeKachah 5637, ch. 87.
- (Back to text) The above series cites the Sefer HaLikkutim LehaAriZal
which points out that the Hebrew word esrog is an acronym
for the verse, "Let not a trace (lit., 'the foot') of
pride come upon me" (Tehillim 36:12).
- (Back to text) Sukkah 35a.
- (Back to text) Avos 4:1.
- (Back to text) The theme of unity is also emphasized by the mitzvah of
sukkah. As our Sages teach (Sukkah 27b), "All of Israel
are fit to dwell in a single sukkah." (See the essay
which follows.) However, while the sukkah highlights the
collective nature of our people, the mitzvah of lulav and
esrog relates this togetherness to each one of the
individuals who comprise this collective.
- (Back to text) See the above essay entitled "At One with G-d; At One
with our Fellow Man."
- (Back to text) See the explanation of the second dimension of unity in
the above essay.
- (Back to text) Yirmeyahu 31:8.
- (Back to text) Yeshayahu 35:10.