Answer:
   
   [Adapted from Rabbi Eugene Borowitz's [5]Liberal Judaism...]
   
   As described elsewhere in this FAQ, Reform Jews believe that human
   beings are responsible for both the Written and the Oral Torah. The
   sacred texts and contemprorary sages have much to teach us, but do not
   legislate for us. Reform Jews insist on the freedom to determine for
   themselves the aspects of faith they will continue to observe, and
   what in their belief requires the creation of new forms.
   
   This freedom can be broken into two periods. The first period,
   sometimes called "Classic Reform", runs from the start of Reform
   Judaism until around the 1960s. It can be characterized by the notion
   of what Rabbi Borowitz calls "negative freedom". In other words,
   Reform Jews of this time defined themselves by their right *not to do*
   what traditional Jews considered mandatory.
   
   Beginning in the 1960s (although there were elements as far back as
   1920) and continuing to the present day is the period of what is
   called Modern Reform, and Rabbi Borowitz characterizes as "positive
   freedom". In other words, today's Reform Jews use religious
   self-determination to add to their religious observance. Previously
   rejected or neglected traditions are readopted, and new ones are
   created to express growing Jewish sensibilities. This is reflected in
   the 1999 [6]Statement of Principles
   ([7]http://www.ccarnet.org/platforms/principles.html).