From Russell Kirk's The Conservative Mind:

Radicalism since 1790 has tended to attack the prescriptive arrangement of society on the following grounds:  

(1) The perfectibility of man and the illimitable progress of society: meliorism. Radicals believe that education, positive legislation, and alteration of environment can produce men like gods; they deny that humanity has a proclivity toward violence and sin. 

(2) Contempt for tradition. Reason, impulse, and determinism are severally preferred as guides to social welfare, trustier than the wisdom of our ancestors. Formal religion is rejected and various ideologies are presented as substitutes. 

(3) Political levelling. Order and privilege are condemned; total democracy, as direct as practicable, is the professed radical idea. Allied with this spirit, generally, is a dislike of old parliamentary arrangements and an eagerness for centralization and consolidation.

(4) Economic levelling. The ancient rights of property, especially property in land, are suspect to almost all radicals; and collectivistic reformers hack at the institution of private property root and branch.

(5) Radicals unite in detesting Burke's description of the state as ordained of God, and his concept of society as joined in perpetuity by a moral bond among the dead, the living, and those yet to be born--the community of souls.