The Carter Policy had simply stated, without much specification in the unclassified version, that "The United States will pursue Activities in space in support of its right of self-defense." Reagan's space policies made similarly general statements. Clinton's top goals were to "enhance knowledge of the Earth, the solar system and the universe through human and robotic exploration" and to "strengthen and maintain the national security of the United States." The Clinton space policy, like the space policies of Carter and Reagan, also stated that "The United States will conduct those space activities necessary for national security." These activities included "providing support for the United States' inherent right of self-defense and our defense commitments to allies and friends; deterring, warning, and if necessary, defending against enemy attack; assuring that hostile forces cannot prevent our own use of space; and countering, if necessary, space systems and services used for hostile purposes."