The primary purpose of the seder-night service is to inculcate our descendants with proper education, to deliver the torch of Torah values unto posterity. The keyword of the seder-night is "Vihigadita Lebincha" (Shmos 13:8), tell your progeny!
It is insufficient to just "show" a practical example of Torah practice - one must deal in oral discussion, the give-and-take of question and answer. This mitzvah of education is truly all year long "Veshinantem Lebanecha," and comes before the mitzvah of "Vedibarta Bam" (Dvarim 6:7). This is because Torah study is an ongoing process, constantly in action. It is not just introspective but it entails delivering unto others, guaranteeing permanency. This point is imperative especially as regarding children. The characteristic of youth is to question, they take nothing for granted. One indication of premature old age is the blase attitude of disinterest, an aloof disregard for all worldly matters not directly attached to one's individual welfare or close circle of interests. The younger one is, the more one marvels at the beauties of nature, at a butterfly or at a tiny beetle. The older (in spirit) one is, the more he reacts with a yawn of boredom, so to say, answering "so what?". This bland response is considered "sophistication". The Torah attitude, however, is to be constantly delving, hence we have sources that tell us "There is not a Bet Midrash session without a chidush" Hagiga 3a). Any question asked is similar to a spade unearthing marvelous mental treasures.
With this focus on the important role of questions within Judaism in mind, there are four basic questions asked during Seder night: The famous "Mah Nishtana". The first one is: Why on all nights of the year we may eat regular bread, but this Pesach night only Matza? The answer is that we left Egypt hurriedly and couldn't wait till the yeast leavened. We ate in haste (Shmos 12:11). Since we were banished is a haste (Dvarim 16:3). The "Missilas Yeshorim" (beginning of Chapter IX) teaches that we are similar to soldiers on the battle front, who have no time to put spices or seasoning in their food. They eat impromptu, since they have matters of great importance to deal with. So too, if all year long we may occasionally eat tasty bread, salted and leavened, when we have to keep an alert mind, when we have to be vigorous in spiritual activity (as we were upon exiting from Egypt on our way to Israel) then we eat simple and plain fare for we have a sublime and significant task before us: to praise the Lord for His wonders!
The second question is why all the year long we Jews sometimes eat general green produce and sometimes bitters. But for Pesach night, the major ceremony is to eat bitters! The answer is given by Rabbi Shimshon Raphael Hirsh ("Haggadah" published by Feldheim, p. 71): "Jewish thinking realizes that it is far easier to trust in G-d during dark prospects than it is to remain faithful to our obligations in the bright sunlight of success". Many are those who derelicted their duties due to riches, honor, fame or general well-being. The bitterness of salt only increases culinary appetite. The problem of ascending a steep mountain only increases physical proficiency and causes sturdier muscles and stamina. The fact that the great majority of Jewish history is replete with stories of persecution, with fantastic chronicles of international anti-Semitism, only underlines the credo "stress causes success, duress causes durability". Our ability to chew on bitters and yet survive (we are the oldest nation in the world) shows our G-dly inner spark.
The third question is, why all the year long don't we always immerse foods in relishes, but Pesach night we do this twice! The answer to this is to recognize the implication of reliance upon G-d (Bitachon). The point is that the child asks "Mah Nishtana" since immediately following "Kiddush" and the first goblet of wine, he was given "karpas" as an appetizer. Nevertheless, immediately when the matzos should be eaten, (as is the normal process after every Yomtov Kiddush,) these matzos were covered and concealed (before the "maggid" part of the Seder ceremony). Having his appetite aroused and then to be denied food appears most odd! So too the bitters are dipped into the sweetener (Charoses), but then the sweetener is shaken off so that the taste of the bitters should not be canceled or altered (Shulchan Aruch 475, paragraph one). What is the logic of these contradictory acts?
The answer is that G-d satiates all recipients of His bounty with "satisfaction". (Tehillim 145 verse 16). The "Noda Bi'Yehuda" asks why doesn't Psalms say "G-d gives food" or "sustenance" or "providence". Of what good is psychological "satisfaction"? The answer is that no matter if a person has much material riches, or if he has only minor finances, if he has "Ratzon" (satisfaction) he is constantly blessed. Rabbi Hanina ben Dosa only had carob fruits but it was "dy lo", enough for him. He did not request more. (Ta'anis 10b). True we have the ability to eat matzos immediately following Kiddush. We also have the ability to eat the bitters together with the charoses sweeteners. But we are "above it all". We are not slaves to physical desires.
The fourth question is why all the year long we sometimes recline (on sofas) and sometimes sit erect (on chairs). but Pesach night we all lounge on sofas as if we were Kings! The answer is that in ancient Egypt commoners were considered to be rabble. The majestic monuments, the pyramids that we see today only attest to superb engineering prowess. The ancient Egyptians had great skill in harnessing the forces of nature so that the overflow of the Nile River would bring great productivity to adjacent agriculture. The marvelous aqueducts, the myriad channels dug into the ground alongside that Nile show great acumen. However, what was individual human fortune then? Nothing. All were slaves. the entire nation, officers, courtiers, soldiers, merchants, all were drawn down into the morass of king-worship. Pharaoh himself knelt in worship to the deity he believed resided in his breast. The lash, the chains, the instruments of torture, these are the true emblems to the great achievements of ancient Egyptian culture. But G-d willed otherwise. His miracles proclaim that humans are not supreme. Using science and harnessing nature with technological advances is just not enough. Man is to be free, to be reclining as master of his body and of his soul. This freedom is what we proclaim on Pesach night. We teach that the true "Ben Horin" is he who observes divine dictates (Avos, Chapter VI). The ultimate question is if man is to be pulled and pushed by his evil instincts, or if his divine spirit, his soul will overcome.
The word "Pesach" (in Hebrew) means "to jump", "to hop". Just as G-d hopped and passed over the houses in Egypt, so too we must skip, hurdle and jump over our animalistic tendencies. We must not be bedazzled with civilization's great progress. True we have wonderful technologies, but unless used properly they easily lend themselves to war casualties and terrorists. Without Torah, humanity suffers.