The truth is not always useful, not always good. It's like putting your faith in water. Yes, we need the rain, but too much can sweep you away in a flood and drown you. Like all great natural, elemental forces, the truth needs to be channeled, managed, controlled and intelligently, morally allocated.
The quote suggests that while truth is essential, it can also be dangerous and overwhelming, much like water. Truth can nourish and provide clarity, but excess truth can be harmful, potentially leading to destructive outcomes. This idea likens truth to a natural force that requires careful handling to avoid negative consequences.
Iain M. Banks emphasizes the need for wisdom and responsibility in managing the truth, implying that it should be distributed thoughtfully and ethically. Just as water is vital for life yet can flood and devastate if not properly managed, so too must truth be approached with caution and respect for its power.