Disclosed herein are soft and stiff compositions, i.e., compositions which have a flexural modulus that is greater than the value that is expected based on the composition's hardness. The compositions preferably have a hardness/modulus relationship represented by the formula H≦11.889 Ln(M)+42, where H is the hardness of the composition, in JIS-C, and M is the flexural modulus of the composition, in ksi; or a softness/stiffness relationship represented by the formula if M