Thought lines represented a philosophy encompassing both individual and shared perspectives within the Vak species. The Vak, who were native to the planet Primea in the Unknown Regions, placed great value on every thought line when it came to making decisions for their society. Other species sometimes ridiculed the Vak Combine because their decision-making process was relatively slow. Despite this, nearby nations were careful to avoid killing any Vak during battle, as harming even one Vak would rob the entire Combine of that individual's thought lines, which would be interpreted as an act of aggression against all Vaks.
The concept of thought lines was introduced in the 2020 novel Thrawn Ascendancy: Chaos Rising, which is the initial installment of The Ascendancy Trilogy written by Timothy Zahn.