This post contains the answer to the question posed in the post where the clothes are the person must also be.
I encourage you to try and solve the questions posed in the prior post before reading the answer.
Crime is common. Logic is rare. Therefore it is upon the logic rather than upon the crime that you should dwell. – Holmes
Lestrade has established a valid argument. The argument in a more structured form could be stated as follows:
|hypothesis||If the clothes were found by the river then the body must be in the river|
|observation||The clothes were found by the river|
|conclusion||Therefore the body must be in the river|
Lestrade also thought it was a sound (or at least a highly probable argument) based on his actions. He has found the clothes by the river. Based on this evidence (or observation), Lestrade started dragging the Serpentine River looking for a body because of his working assumption that his hypothesis (see table) was true.
However, Holmes frustrates the detective by pointing out (though the argument is valid and the conclusion is probable) there is a faulty assumption Lestrade is making.
Holmes argument could be stated in a more structured form as follows:
|premise||A person is always found near their clothes|
|premise||their clothes (or most of them) are in their closet|
|conclusion||Therefore the person is in the closet|
Lestrade assumes that the clothes being found by the river would be an indicator that the body would also be found nearby. While not committing any formal fallacy, Lestrade is close to committing the fallacy of the converse accident by forming his hypothesis as a general rule that will be true in all circumstances, rather than one of several possibilities. His generalization, even if based on his actual experiences as a detective, will turn out to be incorrect.
If the hypothesis Lestrade accepted was correct, then he would have a more probable chance of success in finding the missing bride by looking in her closet.
This is a good illustration reminding all of us that a valid argument can turn out to be false. While it can be argued that it is probable that the body was in the river, the clothes could also have been placed by the river for a variety of reasons that do not include the body being in the river as the rest of the story shows to be the case.