Is death to be welcomed or feared? Is the priority the living or the dead? The Jewish tradition incorporates all these points of view. In some communities the anniversary of death is marked by fasting and in others it is celebrated with a toast 'to eternal life'.
Biblical law is scant. When Abraham comes to mourn Sara and to cry over her (Genesis 23), we are not told if he is crying for his loss or hers. Rachel's nurse, Deborah, dies and is buried under the 'Tree of Tears' in Genesis 35 but it is not until the deaths of Aaron and Moses that the community mourns for thirty days.
Sitting on the ground (or on low stools) and symbolically tearing ones clothes, removing ones shoes, all go back to biblical custom. It is the Talmud that formalizes the laws that still apply today. During the first Seven (Shiva) Days one remains at home to be visited and comforted by the community. For thirty days (Shloshim) one may not celebrate, listen to music, shave or wear new clothes. Only for a parents demise does this process last for a whole year. As does the custom of actively participating in daily service by saying the Kaddish which is not a memorial prayer so much as a celebration of life. Some suggest this is to help the soul ascend. Others say it simply compensates the community for the loss of one of its members, by reinforcing commitment.
The Shiva is the start of the mourning process. It acts as a ritualized transition from burial, shock and pain towards rehabilitation. It allows for cathartic display instead of withdrawal and suppression. It enables the community to rally round and express its solidarity and help feed and provide for the mourners during all seven days. For some it is often suffocating and an endurance but for most it is therapeutic.
In the Book of Job the mourners did not start speaking until Job invited them to. In theory that remains the case but in our world of easy words and banter the single most problematic aspect of the Shiva is the well meant but often ludicrous attempt to explain or justify the loss and give glib answers. The Talmud insists that one recognizes and accepts God in loss as in joy. In the words of Job, 'God gives and God takes.' The purpose of visiting the mourners is to express love and solidarity rather than theological certainty.
In fact, Judaism has always given priority to life, 'Only the living can praise God'. The dead have moved on to a better place. Or if according to Maimonides, they had no expectation of Life After Death, then in fact they have simply died and that is the end of it. Talk of Heaven or Hell is merely a metaphor. The dead live on in our memories and their legacy is the way we live.