Humanity has reached a point in evolution where any significant, moral progress will necessitate a true alliance between the theories of  science and religion, yet we continue to struggle with many disparities between them.  As Kardec explains, the revelations of Spiritism will be the key to closing the gap between these two "levelers of human intelligence."

Below is an excerpt from "The Gospel According to Spiritism"¹, in which Kardec addresses the topic of this "alliance between science and religion." 

Science and religion are the two levelers of human intelligence. One reveals the laws of the material world, the other the laws of the spiritual one. Now, since these laws stem from the same first cause, which is God, they can't contradict each other. If they did, it stands to reason that one would have to be right and the other wrong, which would be inconsistent with the divine design. Consequently, the apparent incompatibility that exists between science and religion is simply the result of incomplete views of the world and one-sided positions taken by both parties. This conflict of ideas has often given rise both to unbelief and intolerance. 

 The time has come, however, when the teachings of Christ can be interpreted in their fullest significance. The veil of allegory that he purposely used on many occasions must be lifted. Science must see beyond matter and acknowledge a spiritual perspective; religion must stop ignoring the fundamental laws of matter. Only in this way will both sides come together and learn to lean on each other. As a result, religion will no longer be discredited by science. Its accordance with reason and with the compelling logic of the events of nature will give religion a new, unshakable power.  

Until our own day, science and religion have struggled with their differences. Each has had a tendency to see matters only according to its own particular point of view, and each has rejected the other. Clearly, something more was needed- something that would allow these two realms of knowledge to close the gap between them. The missing link is contained in the knowledge of the laws that govern the non-physical (spiritual) realm and its interactions with the world of matter- laws, it should be pointed out, as constant as the ones that govern the movement of the stars and the existence of living beings. Once these interactions are empirically demonstrated, we will see things in a new light. Faith will speak to reason; reason will find nothing illogical in faith; materialism will be overcome.  

Nevertheless, in this case as in many others, there will always be those who initially choose to stay behind. They might, for a while, resist the new views, but they too will eventually be overtaken by this new wave of progress. A new moral revolution is taking place whose foundation has been maturing for over eighteen centuries. Directed by the higher intelligence of the spirit world, this silent revolution, which will bring about a new era for the human race, now nears the completion. Its consequences are easy to predict; the new order will produce inevitable changes in all aspects of social relations. We say inevitable because no one will be able to circumvent these changes; they are part of the designs of Providence, a natural by-product of the Divine Law of Progress.