Naïve realism
Naïve realism is a phrase coined by Stanford University psychology professor Lee Ross, referring to a common sense theory of perception. Most people, until they start thinking philosophically, are naïve realists. This theory is also known as "direct realism" or "common sense realism".
Naïve realism holds that the view of the world that we derive from our senses is to be taken at face value: there are objects out there in the world, and those objects have the properties that they appear to us to have. If I have an experience as of a large apple tree, then that's because there's a large apple tree in front of me. If the apples on the tree appear to me to be red, then that’s because there are objects in front of me – apples – that have the property redness.
In other words, naive realism claims that the world is pretty much as it appears to our senses. All objects are composed of matter; they occupy space, and have properties such as size, shape, texture, smell, taste and colour. These properties are perceived directly. So, when we look at and touch things we see and feel those things themselves and so perceive them as they really are. Objects continue to observe the laws of physics and retain all their properties whether or not there is anyone present to observe them doing so.
Plausible though naïve realism may be, it has serious problems, among which is the problem of the variability of perception. The same object may appear differently to different people, or to the same person at different times. The apples may appear to be red in the daytime, but at dusk they are a shade of grey. If naïve realism is to be taken seriously, and colours are out there in the world, then apples regularly change colour depending on how much light is around them. It is much more plausible, though, to think that the apples are the same as they ever were, that all that has changed is our experience of them.
Naïve realism is also used as a synonym for realism, the belief that physical objects continue to exist when they are no longer perceived.