How did Christianity affect western civilization?

Part of the contribution of Christianity to the decline of the Roman Empire is economic, and this part was indirect, since it was within the power of the Christian emperors to act as they did. Constantine's financial assistance to the Christians was grossly disproportionate to their numbers, particularly during the early part of his reign. This effectively resulted in a transfer of wealth from the majority of citizens to a privileged elite. The swingeing taxes needed to support this largesse also resulted in a loss of motivation for the middle classes, and this a decline in prosperity. While economics was not yet a field of study in the time of Constantine, it is now recognised that the massive expenditure that Constantine incurred, and the legacy that he passed on to his sons and successors, were an important contributing factors in the decline of the Roman Empire.

A further factor was the decline in education and, with it, the decline in the skills necessary to maintain a thriving empire. The Christian Church held that education was only necessary if it helped in meeting the needs of the Church. Eventually, even kings were often illiterate. Because the Church was suspicious of all texts associated with paganism, the ancient texts were destroyed, with even the fabled Library of Alexandria burnt. The eventual rediscovery of the ancient philosophical texts and the re-emergence of science and mathematics resulted from the successes of the Muslims in Spain and elsewhere.

It should be understood that there were other factors that also led to the decline of the Roman Empire and of western civilisation, and that many of these factors were entirely outside the control of the Christian Church. The Roman Empire is believed to have already been in decline by the time of Constantine. His policies, and those of his successors, hastened that decline, but whether Christianity was the major reason for the fall of the Roman Empire continues to be debated.