I must confess that I'm not too familiar with the concept of forms, and Wikipedia was not entirely helpful on the subject. Mick, if you don't mind, could you answer a few of the questions I have?
How do we know what a form is?
*If we only see the shadows in the mouth of the cave, how can we tell anything of the complexities that may not be shown in the silhouette? E.g. what can the shape of a giraffe tell us about what a giraffe actually are (that, for instance, biology cannot)?
*How can we know if there are any such complexities at all, and that the shadow is not a complete representation of the form? E.g. how do we know that the form of a giraffe doesn't happened to be the "perfect" form a giraffe?
*How do we know if two shadows that look completely different are not outlines of the same form from different angles? E.g. how do we know that "deformed" giraffe actually diverges from the form of giraffe, and not simply is another aspect of it? How do we know which one is (the most?) correct?
*How do we know that two shadows that look the same are not of different forms? E.g. how do we know that there is a form for giraffe, and not simply a form for each individual giraffe that happens to be very similar to each other? Then how can we tell if a giraffe is deformed?
*Are concepts formed in the mind also just shadows of forms? Either way, how can we tell the difference between the human understanding of a form and an arbitrary human-invented category?
*Finally, how do we know that the shadows actually represent forms at all? Why can't the forms be something completely different that we only may glimpse some faint details of, e.g. how do we know that the fundamental forces of physics isn't the basic forms? How can we tell that there is something casting a shadow rather than that the "shadow" is in fact the entire object?
How does form interact with matter?
*Is there any observed occurrence of form interacting with matter? If so, what? Interaction with matter is, more or less by definition, a change of state in energy and/or matter, so it should be possible to measure.
*Does form interacting with matter obey the first law of thermodynamics?
*What different interactions are available for molecules/atoms/fundamental particles when they are arranged in the form of a rock and when they are not? How are the possible sets of interactions imposed on molecules/atoms/fundamental particles depending on what form they adhere to?
*How does the form of a circle affect the paper and ink when I draw a representation of a circle? What is the fundamental difference between ["draw a circle" compared to "draw a squiggly line"] and ["draw a squiggly line" compared to "draw a different squiggly line"]?
*What extra functions does your web browser gain by being in the form of a web browser (rather than say a word processor) that wasn't anywhere in its lines of programming?
*And, correct me if I'm wrong, you seem to be saying (
here for instance) that science will only push the question further back. How can you be certain that it is forms that fills the gaps, rather than anything else (or, indeed, that we do or can know what fills them)? This sounds very much like a god-of-the-gaps argument, although I guess I should call it forms-of-the-gap in this case.