Where a commercially operated ship is damaged in a collision, an important element of the owner's claim against the other vessel is likely to concern lost profit. Whereas the cost of repairing a partially damaged ship can often be agreed within tolerable limits between attending surveyors, and the cost of replacing a total loss can usually be agreed within a narrow margin between the parties' sale and purchase brokers, when it comes to claims for loss of profit it is highly likely that there will be a dispute. Disputes over establishing and quantifying a loss may arise from difficulties of evidence, or in setting a rate or period for a loss, or in assessing the likelihood of future events; and may also be triggered by economic cycles, a failure to mitigate a loss, or by events subsequent to a collision. A particular feature of the early cases was the search for certain, or virtually certain, loss, as distinct from merely likely or even probable loss, which was regarded as speculative. This had an impact on losses that could be sustained in the future; and, as will be seen, it was only gradually, as the safety of ships increased and the terrors of prognostication diminished, that courts began to consider such claims.