Other mechanists have argued that the covering law model is too strong. Philosophers of biology have long argued that there are no laws of the sort the logical empiricist described in biology and other special sciences (Beatty 1995; Mitchell 1997, 2000; Woodward 2001). One might conclude from this that there are no explanations in biology (Rosenberg 1985), but such a radical conclusion is difficult to square with obvious advances in understanding, e.g., protein synthesis, action potentials, cell signaling, and a host of other biological phenomena.  In such cases, one finds that scientists appeal to mechanisms to do the explanatory work, even in cases where nothing resembling a law appears to be available.