Speaking and writing is a kind of practice governed by man's mind. When people use language or words to express their thought, there are logical relationships such as "and, not, or" between multiple sentences. The statements connected by these logical relationships are called logical constructs or logical structures. A logical construct of sentences describing something is a simulation of something or a thought game. Some of the structures and properties of this logical construct are the same as the objective real things, and some of the structures and properties are different.

The basic elements of logical constructs are symbols. There are many kinds of symbols. Words, numbers, graphics, animations are symbols, sounds, language and actions may be symbols, too.

A symbol has three characters. First, it is a man-made substance, not a consciousness. Second, when we see or hear it, we'll have certain associations in mind. Third, the properties of the symbol itself have no value, while the associations we make in mind when we see and hear it have a lot of value.

A logical construct usually consists of multiple sentences. Russell called each sentence an atomic proposition, and multiple sentences constitute a molecular proposition. For example, China has a long history, and China has great people. This is a molecular proposition consisting of two atomic propositions. Molecular proposition is a logical function composed of atomic propositons. An atomic proposition can be its own logical function. Multiple molecular propositions constitute documents, theories, books, and systems of thought.

The logical construct composed of symbols is substance, not consciousness. But when the logical construct is constructed, processed and used, the corresponding consciousness needs to be produced. The symbol is dead, and the consciousness corresponding to it is alive. So the main function of logical construct is that of consciousness.

Definition: Logical constructs are simulated or innovative thought products, including thought products as consciousness and symbols.

There are three forms of logical constructs as thought product. The first is composed of multiple statements and propositions. The second is composed of multiple images, videos and so on. For example, when we think of China, we think of maps of China, the Great Wall and Huanghe river. These images and videos can also be connected into a complete logical construct by logical relations such as "and, not, or" like propositions, in which each image or video is equivalent to an atomic proposition. The third type is composed of statements, propositions, images and videos.

Objective things have many properties, some properties can be simulated by image and video, some properties can not be simulated by image and video. For example, the weight of product cannot be represented by images, but only by literal symbols. The shape of the product is difficult to describe clearly with words, but suitable for graphic description. So the simulation needs both image and language. The combination of these things with logical relation words is a complete logical construct.