We ask whether the recently discovered superstring and superfivebrane
solutions of D=10 supergravity admit the interpretation of non-singular
solitons even though, in the absence of Yang-Mills fields, they exhibit
curvature singularities at the origin. We answer the question using a test
probe/source approach, and find that the nature of the singularity is
probe-dependent. If the test probe and source are both superstrings or both
superfivebranes, one falls into the other in a finite proper time and the
singularity is real, whereas if one is a superstring and the other a
superfivebrane it takes an infinite proper time (the force is repulsive!) and
the singularity is harmless. Black strings and fivebranes, on the other hand,
always display real singularities.Comment: 15 page
