You are dead. It stands for "true art" and "science" and without it you are dead. Einstein spoke these words not about physics or a religion but of the human experience of mysteries. He was a "religious man" and his religion was that mystery. Einstein was taken by knowing the unknown, he was striven to learn more about nature and "the marvelous structures of existence".

I suppose that without a need for wonder a person is symbolically dead. He or she no longer seeks the mysteries of life, and to Einstein the mysteries lead to a pursuit of knowledge. And with no seeking of knowledge a person might as well not be alive. When it is no longer important to grow as an individual the individual begins to die. Many have shared this need for understanding mystery and without it many of the things that we have today would not exist. It is this need for knowledge that is the source for improvement in not only our society but for the most part the civilized world. It pushes people further to think and test what we know and find better truths.