We investigate several fragments of multiplicative linear logic, in a
natural deduction setting and with the aim of a better understanding o
f the par connective. We study, first, a pre-tensorial calculus, which
is strengthened then in the standard tensorial fragment. The addition
of a further pre-tensorial connective yields (a natural deduction ver
sion of) Full Intuitionistic Linear Logic. A further strengthening of
the rules leads to the full classical multiplicative logic. Some proof
-theoretical properties of the systems are investigated.