Final answer:
The observation of an individual igniting a fire is considered direct evidence, which supports the truth of an assertion without needing inference, unlike circumstantial evidence.
Step-by-step explanation:
The observation of an individual igniting the fire would be considered direct evidence. Direct evidence supports the truth of an assertion directly—without an intervening inference. This is different from circumstantial evidence, which requires an inference to connect it to a conclusion of fact. For example, direct evidence in a chemistry context can be observing a chemical reaction like a match burning, which is evidence of the match's flammability, a chemical property. In law, witnessing a person commit a crime provides direct evidence of their involvement. Circumstantial evidence would be something that suggests a fact by implication, such as finding a matchbook at a crime scene which might imply that the person who left it there could have started a fire.