I think your watch is slow and you think mine is slow in the following sense. For each of many events, I record their time t and position x while you, moving relative to me at constant velocity, observe a different time T and position X. Between two events with the same X-value, such as ticks of your pocket watch, the difference in t-times is larger than the difference in T-times by a factor gamma. Conversely, between two events with the same x-position, such as ticks of my pocket watch, the difference in T-times is larger than the difference in t-times by that same factor gamma.<p>There is no contradiction because events with identical x-positions do not have identical X-positions.<p>If you already know what a partial derivative is, see the first paragraph of this: <a href="http:&#x2F;&#x2F;mathpages.com&#x2F;rr&#x2F;s4-07&#x2F;4-07.htm" rel="nofollow">http:&#x2F;&#x2F;mathpages.com&#x2F;rr&#x2F;s4-07&#x2F;4-07.htm</a>