The purposes of this research were to study the development of ability to identify the sources of childrens beliefs by seeing, telling, feeling and inference and to compare them with the different levels of reasoning-oriented child-rearing pratice. The subjects were 160 kindergartens 1-3 and Prathomsuksa 1 pupils (3 - 6 years old) by Multistage Random Sampling from private schools in Bangkok Metropolitan area. The instruments for collecting data consisted of two sets : A questionnaire of reasoning-oriented child- rearing pratice and the test of ability to identify the sources of their beliefs. The test was devided into four tests according with type of sources:seeing, telling, feeling and inference. The data were analyzed by Chi-square test, Cocharn Q test and McNemar test. The results were as follows : 1. The development of the ability to identify the sources of their beliefs by seeing were found in the children at the age of four

be feeling and inference at the age of five and by telling at the age of six. Their ability was significantly found to increase by age. 2. Three, four and five year-old childrens ability to identify the type of sources of their beliefs was significantly different. But there were no differences in the children at the age of six. Three year-olds ability to identify the sources of their beliefs by seeing was significantly different from that by inference. Four year-olds ability to identify the sources of their beliefs by seeing and feeling was significantly different from that by inference. Five year-olds ability to identify the sources of their beliefs by seeing, feeling and inference was significantly different from that by telling. 3. The level of reasoning-oriented child-rearing pratice significantly correlated with the ability to identify the every type of sources of their beliefs but seeing. The children from higher reasoning-oriented child-rearing pratice families significantly performed better than those from the lower reasoning-oriented child-rearing pratice families in the sources of beliefs by telling, feeling and inference.