The participants' planning and instruction addressed various aspects of the nature of
science, including tentativeness, creativity, subjectivity, the use of indirect evidence in the
construction of scienti®c models, and observation and inference. For example, one participant
described a lesson where she taught the tentativeness of scienti®c explanations by using a ``black
box'' demonstration. In this lesson, she provided her high school biology students with
experiences that emphasized the need to modify inferred explanations when new data become
available. Additionally, she encouraged her students through class discussion at the conclusion
of the lesson to relate this concept to the tentative nature of scienti®c theories in general.