After observing people through the lens of extraversion and introversion for a while, Jung came to realize that it wasn’t just an orientation to the inner world or outer world that made people different from each other. It was also important to consider what mental activities they were engaging in when they were in these worlds. Jung called these mental activities functions, based on the “function” being performed. Now they are frequently referred to as mental or cognitive processes. Jung described four cognitive processes and said that every mental act consists of using at least one of these four cognitive processes. Furthermore, these cognitive processes are used in either an extraverted or introverted way, making eight processes.
The Eight Cognitive Processes Adapted from Linda V. Berens and Dario Nardi, Understanding Yourself and Others®: An Introduction to the Personality Type Code (Telos Publications, 2004)
Ti - introverted ThinkingAnalyzing; categorizing; evaluating according to principles and whether something fits the framework or model; figuring out the principles on which something works; checking for inconsistencies; clarifying definitions to get more precision.